Another answer after OP's clarification.
I still can't bring myself to believe that without biology change you would achieve your cultural shift. But let's hand-wave this and assume that a society like that exists and think how it would have came to be like that and see where it leads us (because it is fun). In meantime I hope it will provide the answer to OP's questions or at least some useful thoughts or ideas.
So I assume next things:
nepenthe - is a relatively easy-obtainable plant, which is not normally edible so the biological evolution of humans took place the same way as in our world, then relatively recently it was discovered that it has OP's effect on human males.
nepenthe's effect lasts for no longer than a couple of weeks until it dissolves from body, then the victim can remember everything or almost everything that has happened to him.
you can relatively easy make a liquid extract of nepenthe plant in order to add to victim's food (so you don't have to add the raw plant itself) but it requires significant knowledge and equipment to make gas (so you still can make a weaponized form in military facility but not in your garage equivalent)
magic can be used by both genders, but doesn't allow to be immune to nepenthe's effects. Also men can control golems and be a magic user in general (but may not have access to magic items, knowledge etc)
So a country Kramain was founded in year 300 CE which is the same as a country in year 300 CE would have been in our world. In year 367 CE a relatively common plant was discovered to have an interesting effect on males only. It was called nepenthe. Since then the cultural shift has started to form in Kramain. Men who controlled everything has started doing strange things like giving away cattle for free, doing work for free, killing their entire families and doing strange things in general.
It has quickly become apparent that men can no longer do business and make any serious decisions, at first women in their households have been given the obligation to be present at all important decision making times to verify sanity of men. Soon it happened so that all of the business had to be conducted between women to exclude fraud and other issues related to the drugged men. After some time it led to a situation that women has become household masters and got the real economic power. Which in turn let to cultural shift to matriarchy (in whatever meaning you put in it). Along this shift some other things has become more apparent - more women were needed as only women could have been trusted with dealing with mistress' children, especially females. So the cast/order of guardians was born, these women had to be childless and serve to the mistress, protect her from manipulated household males and other enemies. On the other side man started to avoid accepting food from outsiders and especially share meals with women. It has become customary to carry a box with a lock when traveling to keep the food which was prepared by household members or by the man himself. This box had to be locked at all times and key had to be kept very securely. A lot of outside household interactions of men had to be made with a presence of women to protect from drugging effects. After some time cultural norms were adopted which would discourage or prohibit usage of nepenthe.
Men still were used for manual labor and for military service. All under supervision of women. They started to feel oppressed but that was a natural order of things. Marriage in the form we know it dissolved from top of the society to bottom. While richest women would pick their lovers to stay with them for some time either to be a toy or to produce offspring they didn't posses any material rights in household. For poor people it was a bit different and was more resembling marriage but women had the right to 'let' the man go as they seen necessary. This made men even more dependent on women. Wealthier men were educated in craft and basic sciences and women were also getting business, political and military education. Men were taught to obey women.
On the outside men has become more silent and obedient, they didn't talk back to women, they were told to not speak on important matters. In order to get a good place for their sons (basically to let them stay by marriage women for longer, where they were financial responsibility of those marriage women), rich women started to train them in music, dances, poetry, painting etc. On the inside evolutionary aggressiveness and male traits were still present, although somewhat suppressed it had still to get a way to let the steam out which was usually done by bullying weaker men.
At some point a way to create magic golems was discovered and rich women has started to keep these along with female guards from guardian cast to protect themselves from dangers. In year 534 when everything was already under control of women in a local war which was fought under command of female general Luise and has consisted of 500 untrained man foot soldiers and 100 women cavalry, the enemy has used nepenthe in gas form. While the cavalry was away from foot soldiers, foot soldiers were brainwashed to attack their allies after being gassed and told the 'truth' about the sides of this war. General Luise was herself tortured and killed by foot soldiers which then went into slavery with smiles on their faces, and only a handful of cavalry survived and fled to tell the story. After major defeat the way the war was fought changed. To each squad of 10 men there was a woman political attendant attached to quickly refresh men's memory in case of gas attack. In order to keep those women safe to each 5 attendant there was a female golem user attached. It was done to make sure that in harsh conditions of war men would not attack their attendants.
The increased usage and demand for golems put more stain on the economy. Lower classes have been pressed into more poverty and more work. Men started being treated as commodity, more men were sold into other household because of inability to feed them. They became more aggressive because of bad treatment but this was easily suppressed by militia with golems.
In year 943 new threat to Kramain has arised, as men became more and more discriminated but still being quite good in crafts and physical power some of them started to run away from Kramain and form man bandit groups. At first these groups were easy to deal with, but after some time they have started to join forces around a man named Dilak who founded a new religious cult. In this cult women were proclaimed tools of evil, which should be slaves and used only for making more soldiers in order to liberate all the other men. Eating unchecked food was a sin, drugging fellow man was a sin punishable by death, even possessing of nepenthe was a deadly sin. The Dilak cult has started to raid remote villages sacking them and taking or killing men and taking all women into slavery. Them being very agile and small it was hard to fight them off and using gas was expensive and relatively ineffective. Whenever zealots of the cult were seeing or smelling nepenthe gas they would kill themselves, they would never attack in large numbers or directly. They would try to destroy all facilities to produce nepenthe gas and what was more worrisome, the Dilak cult has started to silently spread inside city walls. Followers of the cult started to sabotage work of the cities making them easier to attack.
It was rumored that Dilak is a third son of Dilla, aristocrat in the second largest city of Kramain. As he was the youngest among his siblings, he was raised spoiled by his mother who even gave him a military education which was unheard of at that time. After he started to express some strange thoughts and spoke up at his mothers party, he lost his prospects of getting an invitation to any major house in the country. Eventually even his mother lost interest in him and he was downgraded to do manual labor at his mothers household, he fled. There is no historical record of any of this since records for men were usually not kept as they couldn't inherit.
In year 996 a large scale application of nepenthe was used on men in Kram, the capital of Kramain, to get information on Dilak cult followers withing the city. While it was a great success and more than two thousand believers were uncovered (~1.5% of male population), this has caused a great uproar in masses. It was estimated that in 1015 there was already around twenty thousand believers in Kram, which was around 20% of male population of the city. As number of believers grew, the magic items flow to Dilak cult increased dramatically. Economy started to suffer because of sabotages. The number of female by male victims of assaults has increased dramatically. The cult had invented masks which would delay and decrease the nepenthe gas effect. The Dilak cult has become a major military force and it was estimated that more than 200 thousand women were enslaved by them across the country.
In year 1137 a successful assassination attempt on the queen Lanua, by Dilak cult zealots, marked the end of Kramain as a country.
Well, to be honest, after typing this, I realized that it is not really a direct answer to the OP's question but it was quite fun to write.
I would say, that in my version of OP's universe men would psychologically behave almost as in our world. The main reason for this is that I really doubt that because of nepenthe drug they would be perceived as
fragile. Not trustworthy - yes, fragile - no. So I don't think they would feel physically defenseless.
Since men would be used in manual labor and I think they would retain craft/intellectual/hunt jobs also, so they would still have their ego. I don't think that even in our world in older times women didn't have ego because of financial dependency on men. It was just focused on other things like being pretty (which is of course an effect of dependency). Probably men would have ego in terms of who is the best craftsman or hunter.
Another thing I remembered is, that AFAIK in our world in year ~1000 CE there was not that many marriages for love. In most cases parents would pick up pair for their children, so mothers would pickup marriage(or mating) partners for their daughters, and they would probably look on health, family tree and benefits for household from man, basically the same stuff which was done for son's in terms of wives in our world.