As others have mentioned, there are two schools of thought.
Crisp 4K rendering, no jagged lines, higher details added in textures, etc
Or emulating the look of a CRT by using high density displays to create the same look.
youtu.be/-B5ebucZ69s?si=0lDLAWdMlN77VQen goes into it a bit. This shows off a device for actual consoles. But the same principal applies when doing it in software for emulators.