If the warp is shaped by the belief is the belief in a pleasant afterlife enough to make it so?

Most of the imperium believes when they die they are going to the side of the emperor. Orks believe they will be reincarnated through the Great Green.

How much does this belief actually effect what happens to their souls when they go to the warp after death. And if enough people believed after death they’d go to an actual paradise, then would they?