...and if it is a simulation...
What changes exactly?
Zilch, god is still indeterminable, people are still stupid and society lives on, this is not a question we can answer currently anyway, we do not have the level of technology required to even remotely assert it to the degree that is needed, especially to actually determine what universe is prime, which is also impossible without being a tier 2 or higher civilisation.
Leave this sort of things to philosophy, while we advance a few centuries/millennia.
Another logical problem is that even if we are simulation, then surely on the level required to do such a thing, the simulation would have to be run as it would have if they were trying to simulate their own universe or at the very least with a few tweaks (to determine what would occur if say mavity was a bit stronger or if there were more Iron in the universe than usual), so in essence, we would also be able to run such simulations of our own and perhaps determine if we even are one.
I better stop here, it just doesn't deserve the thought required, but it is more interesting than most of the drivel that passes through.