Indeed,
the main difference between heaven and hell is existential (as a status) - or if you want,
Saint Isaac says the same - but there are also different places. We see this in the parable of the unmerciful wealthy man and righteous Lazarus where our Lord uses a lot of topical (place-ly) adjectives.
Besides that we have enough experiences and stories from the people about the afterlife and nobody talked about a „mixed” place with demons and angels, saints and sinners wandering together just that their internal status is different. On contrary: the depictions were pretty vivid and pretty different.
Also, since we have a 3D body we need to have a 3D place where this body will be after the resurrection of the dead.
No, we cannot experience
fully Heaven/Hell here because - aside of the place - both these statuses imply an intensity unattainable here because of various factors, and, above all, because of time. We are under time / changeability here. However, yes, there are/were saints/people which, with God's mercy, experienced for a (very) short amount of time experienced „heaven” (or „hell”).