This is awesome! Did you use some sort of filter for the PSX look? I really enjoyed the vibe
Some of it is using this renderer https://github.com/pastasfuture/com.hauntedpsx.render-pipelines.psx. A lot is also just rendering the game at a low resolution. You can get a pretty good PSX look just by using low res textures on flat surfaces. The walls are just unity cubes with a textured scaled down in gimp. Then use a render texture to lower the game resolution to something resembling the PSX.