Space is VAST, and many country occupied only a part of it. They do trade and make war just like we do on Earth. On Earth, we have our "peacemaker" between powerful nations in the form of nuclear missiles stationed on land, on submarine, and in aircraft. These tools can deliver death in about 30 minutes to any location on Earth with no real way to stop them for sure. City target and some military target can be targeted beforehand because it is easy to ascertain their location. However, how could we do this for a galactic setting? Unlike Earth, it is possible to keep your home planet hidden and have trades happen on remote planets of no importance. And since planets are far away, all information on a planet would have to be sent using hyperspace links--almost like the underwater telegraph tables of old. This ensures all data coming and leaving a planet can be monitored to ensure no compromising information gets sent out. Not to mention that planets are far away from each other, and even travelling at speed of light, things still take years to arrive. The hyperspace is not faster than light travel, but rather going into a non-euclidean 5th dimension that links two points in 4D space together so it seems the ship arriving destination an instance after they leave their original spot. The warp system jump a vessel very far, nor are the speed of the vessel after leaving the warp faster than the speed it enters warp. In this case, it almost seems impossible that nations in space can effectively deliver unstoppable death in 30 minutes to ensure mutual assured destruction. But what did I miss that could allow this to happen?
Given the two types of spaceship travel you have mentioned there is already the capacity to destroy worlds wholesale, especially if a ship keeps going at the same speed it entered hyperspace and can jump at 0.99c. What you have there is an RKV that can certainly wipe out all life on a planet if not reduce it to molten slag wholesale. RKVs are quite cheap in most settings, it's not starship, it's not even a drone, it's just an engine system strapped to a trigger with a preset destination, it jumps in-system at speed acquires its target and rams home in a flash of hard radiation, run time of the engines should be less than 15 minutes. Price is important because the key to MAD is having enough munitions to kill everyone, everywhere, at any time, to have a MAD scenario in the proposed situation you need at least one RKV for every planet in range of the trading post(s) you use (as well as the trading post worlds themselves) to make sure you get everyone who might be responsible for your overthrow. Make sure you include one for the homeworld too, those closest to you are in the best position to betray you after all. If you know the spectrum of the home star of your trading partner/enemies then you need less weapons to get their homeworld but you still need saturation to make sure you get them all.
Think On Equivalent Scale:
Given a faster-than-light system, I seriously question that an enemy couldn't simply teleport to thousands of star systems and scout out to see who might be located in those systems. Then any piece of equipment that can't be moved (antimatter factories, for example) can be targeted with teleportable weapons. Once you know where your enemy is, game over. And telescopes alone might be able to tell you where big, permanent equipment is located.
I suppose your advanced civilization can live like nomads, constantly wandering throughout space, endlessly rebuilding all their assets for fear of being obliterated. But eventually even the Mongols settled down in the lands they conquered, because ownership of stuff (planets & systems) is still the fundamentals of wealth. If you had a modern empire somehow composed of nomads on ships, nuclear deterrence wouldn't work either. But then, the nomads wouldn't have a base or fixed assets.
While you MIGHT be able to conceal exactly what planet your home world is on, you can't hide the rare habitable planets from interstellar telescopes. ALL habitable planets are hugely valuable real estate, and every one is precious. Unless your empires have completely dissociated distance from interstellar geography, your empire controls a region. Every habitable planet in that region is yours, and a valuable target. So the enemy can simply target every habitable planet in the region you control, and get your home world through process of elimination. The near-light missiles are pre-accelerated and your instantaneous hyperjump allows them to be gated into targets anywhere, even though they aren't pointed at those planets beforehand.
Ah, but what if you've moved your whole civilization into habitats? While you control the region, the people are orbiting stars that don't have planets. The loss of those worlds will be a blow, but not the complete loss that a total nuclear war would be, right? RIGHT?!!!??
The future's equivalent of nuclear weapons are star destabilizers - strange matter, gravity-pulse collapsar bombs, or whatever. It's not thirty seconds, but still just as inexorable. The economy of your empire is ruined quickly by dropping 0.95C bombs (already sped up, cruising through uninhabited space, to teleport to targets on command) on all the habitable worlds, but now an artificial supernova has been set off in the heart of your territory. You can sit back (once you figure out where) and know THIS colony will die in two years, THAT in 15, and within the next century, every star in your empire will be rendered a burned, blasted wasteland. Your entire populous is turned into refugees.
But like nuclear weapons, you eventually have enough planet killers and star killers that you can simply destroy EVERY large body and star within the radius of your enemy empire. Ant the weapons can be easily concealable. Of course, if you know who did it to you, you have near-light bombs and supernova weapons of your own to kill ALL the enemy planets (regardless of value) and stars to render the enemy systems just as desolate as yours. MAD.
Warp the payload
Since you have tech that makes it seem like things arrive at their destination a moment after leaving, you could just load up a ship with an appropriate payload that is capable of going into warp and conveniently arrive on top of their heads before setting off every explosive device you've packed for the journey, effectively instantly nuking everything in sight.
Everyone(as far as I understand your universe) has warp tech so everyone would be able to do this. Possibility of MAD achieved.
Edit: Serial warp the payload
Since warping has a distance limit before needing to cool down, all you need to make the near-instant arrival from essentially any distance possible is to have a stage-based system of warping and shedding the overheated warp engine or whatever is the thing that warp engines need that overheats in the process, similar to how we send rockets up today, only the reason for the shedding will not be because of spent fuel tanks but because shedding mass is the quickest way to get rid of heat in space. Warp, overheat, shed, warp, repeat, kablammo on top of the enemy's head.
If warp engines are too expensive for this to be viable, then simply devise a shedding system where you shed the heat sinks(that have already captured or are capturing the heat) instead of the overheated engines themselves.
Cosmic inflation, redux.
It is frustrating that one cannot immediately wipe out the universe. The speed of light and all. Those people in distant locales will die of lumbago long before my killer deadliness gets to them.
What is real and can affect the whole universe, faster than the speed of light? I can think of only one thing: cosmic inflation.
Inflation was both rapid, and strong. It increased the linear size of the universe by more than 60 "e-folds", or a factor of ~10^26 in only a small fraction of a second!
This speed is possible because it is space/time itself that is expanding, not something moving within space / time.
It has been proposed that the inflation or creation of the universe was an instance of false vacuum decay. https://en.wikipedia.org/wiki/False_vacuum_decay
If our universe is in a false vacuum state rather than a true vacuum state, then the decay from the less stable false vacuum to the more stable true vacuum (called false vacuum decay) could have dramatic consequences. The effects could range from complete cessation of existing fundamental forces, elementary particles and structures comprising them, to subtle change in some cosmological parameters, mostly depending on potential difference between true and false vacuum.
In some scenarios the new lower energy vacuum state could bring with it new physical laws etc. That is exactly what happened with cosmic inflation.
It is usually asserted that a false vacuum decay bubble will propagate with the speed of light. I do not know why that needs to be true. If the first false vacuum decay (cosmic inflation) expanded to fill the cosmos in less than a second, why not this second one. I asked this on the astronomy stack if anyone else is curious.
For this fictional scenario I assert that false vacuum decay would occur as fast as it did the first time with the cosmic expansion. Everything in the universe would be reset in a tiny fraction of a second, again.