With sprites, you can’t add detail that wasn’t there to begin with when projecting at a higher resolution. The Super Nintendo (assuming SNES) emulator’s tools for HD display are filters to smooth it out based on guesswork.
I don’t use smoothing filters for NES/SNES emulated games. I feel that if the game was originally pixelly, it’s supposed to look pixelly. Smoothing edges doesn’t make it look HD, and ruins the font if there’s any text.
On the other hand, it can be Absolutely necessary to have some kind of filter. 640*480 upscaled to 1080p without filters will look terrible, as you’re multiplying the number of pixels by 2.25, and pixels are discrete units. Meaning you’ll have added and removed pixels, making text and whatnot nearly unreadable.
(that said, it seems like the filters for SC:R’s SD mode actually work in windowed mode, vs Fullscreen on a 1080p display, where it feels like they’re trying to emulate a CRT display or something)