Quick Menu > Options (inside the retroarch Menu (hotkey + B ) into the PSX core (in game)
https://retroresolution.com/2016/01/07/playstation-emulation-on-the-pi-enhancing-the-experience-with-the-options-menu-part-two-graphics/
This options:
Enhanced resolution (slow), Enhanced resolution Speed hacks, Enable interlacing are not available.
In recalbox raspberry pi, is available this options... do you know why?
https://github.com/libretro/RetroArch/issues/1395
Intel x86 doesn't have the NEON graphics plugin any longer. It was very buggy and unlikely to be fixed.
How could I improve the graphics and textures of the psx games?
Change the emulator.
The other emulator have an option to change resolution to 1x native, 2x native and more options.