And there will be synergies; how these play out depends on the discretion of the author, so I'll leave these to everybody's imagination.
Also, I'm working off the question as currently stated; the outcome can be affected by more traits - e.g. parts of this answer would shift if due to differences in healing rage, or resilience to parasites and infections, amount of xenophobic tendencies towards their own species (e.g. humans tend to restrict cooperation to humans they consider to "belong to us", Orks may be more or less xenophobic), etc. etc. etc.
Orks require more calories, which is the limiting factor.
Orks typically having twins, not dieing to childbirth and (most importantly) growing up faster means that they reproduce to a land's population capacity much faster than humans, but their overall capacity will be lower than that of humans.
This means that uninhabited areas will be quickly flooded with Orks once they reach it, but once the Orks find human-inhabited land, they will find themselves outnumbered.
It also means that after a catastrophe, Ork population will replenish a few years earlier than human population.
So you get this dynamics:
Orks will get there first, but will start to get driven back - slowly - as soon as they find humans.
After a catastrophe that hits both populations in an area, the Orks will be back to fighting conditions anywhere between 5 and 25 years before the humans, which means that the Orks will overrun the humans. (Exception: A lot depends on how many immigrants the catastrophe-affected Ork and human populations will allow and attract, and in what timeframe immigrants can come and integrate.)
Does not affect the dynamics much, unless with an empire that is long-lived and makes a point of collecting knowledge like real-world civilisations do.
Note that collecting knowledge is not a universal trait of human societies.
E.g. Byzantium was about the only empire that did so for a long time, and it took the Muslim states centuries to (a) catch up and (b) finally overwhelm Constantinopolis with higher numbers.
And building up a high enough knowledge and technology advantage to actually matter is a matter of centuries; I personally think that no society actively worked towards building up knowledge just to gain an edge, there is always some other motivation behind it. (Possibly with an exception in the "Age of Enlightenment", where technological advantage was motivating some but not all of the people who drove that knowledge-collecting frenzy. Once this produced tangible results, states became interested in driving this more.)
Also, a highly intelligent individual won't make any of their intelligence unless the society values the trait, trains them, and can afford to feed them even though they do not contribute to the economy directly.
In societies that do not value intelligence, the intelligent persons will likely use it for their own purposes - become a leader of some sort, i.e. to gain power (be it military or religious), to gain personal wealth (in societies that allow this), or anything else they want.
So the author can freely choose how much of an effect this intelligence ceiling will have.
Note that Orks will still be able to replicate much of human technology; they just won't be able to understand everything, and the poorly or not understood parts of human technology will be considered "human magicks", possibly "filthy human magicks".
More competition, less cooperation means that more Orks will die or be crippled than humans, with obvious consequences for reproduction rate, economical power, battlefield discipline, post-battle recovery rates, etc.
There is a strong leverage, e.g. minimal differences cause small, easily overlooked effects, notable differences cause obvious effects, strong differences cause massive effects.
Still, the author can dial this up or down at will.
It's unlikely that an Ork will connect the dots.
A human with enough intelligence and data may find that out. (The data-gathering part will be the more challenging task, actually.)
Cooperation/competition is a very strong influence, but the author can essentially dial this up or down as intended - minimal differences cause notable effects, notable differences cause obvious effects, obvious differences cause strong effects, etc.
The average ork and the average human are about the same but orks never go past that so you will never have a ork Einstein.to be true ... it means that not only do Humans have Smarter individuals, but also Dumber (in order for averages to work out to be the same) $\endgroup$