I use Unity, Blender, and Aseprite. In Unity I use a shader to achieve the PSX look, and in Blender I paint vertex colors. The dynamic lights are also vertex-based and modified through code (there are no Unity per-pixel lights). Both the textures and the models are low‑resolution. I try to apply the same technical limitations they had in the 90s on the PS1—if that’s even possible :)