Not good, I imagine; IMO part of the magic of a game from the era is that blocky aesthetic. I'm reminded of how Dracula X Chronicles completely sucks all the joy out of Rondo of Blood with ugly 3D models and weird arrangements of the compositions with 'real' instruments (or just a different synth).

The only reason to play that version is the SotN unlock for the PSP and even then, easier to just download the PSX iso.

The PSP SotN was different enough than the NA PSX release, including a new Maria mode (different than the Saturn one), and a new translation (technically better, but retranslates some iconic lines).

Perhaps most notably, the "What is a man?" scene was completely retranslated

I guess if you have/had a PSP this isn't an option but they did release a collection for the PS4 called Requiem that has these changes packed in.

You can play Arx Libertatis today with the assets bought from GOG (Arx Fatalis). The game is really close to UU.

Ultima Underworld also came out before Doom!