Best scaling type for select content?

[Kyo Tanaka]

3D, 2D, etc. i don't know much about these methods or what they do. To keep things simple, when and what should I use?

[Goro san]

2D i use mostly anime 4k
FSR is most universal for 3D stuff
Frame gen obviously higher version = better 99% of the time.

[Space Detective]

In my opinion, going top-to-bottom...

LS1/FSR/NIS/SGSR: These are all intended to be used on 3D games, to upscale them such that they look like native resolution. LS1 is probably the best overall option here, but feel free to experiment to see which option is the best for you in terms of performance/quality balance.
BCAS: I believe this is a variant of bicubic filtering, though I don't recall specifics. I don't use this and don't even really recall how it looks, so someone else will have to fill you in here.
Anime4K: If you're playing a game with drawn artwork, this is basically to them what LS1 and the like are to 3D games. Note however that this can actually be quite intensive (this is for games locked to a lower resolution or look bad when using default fullscreen/resolution options, it is not for performance), and that this doesn't do anything for pixel art.
xBR: This is intended for 2D pixel art, though honestly I hate it for that purpose and don't use it. LS's author once suggested using this on 3D games as anti-aliasing, but I've never tried that.
Sharp bilinear: Basically use this for any games that the other upscalers don't work as well for.
Integer: Very sharp and clean upscaling compared to standard bilinear, but restricted to doing 2x/3x/etc. scaling. Use this if the game you're scaling happens to be exactly half/a third/etc. of your display's resolution (e.g. 720p when you have a 1440p/2K display), or if you want something sharper than sharp bilinear and are willing to accept some letterboxing or pillarboxing.
Nearest neighbor: This is similar to sharp bilinear, but produces sharper results at the cost of creating unevenly-resized pixels; which can cause noticeable aliasing-like issues when the screen scrolls/camera moves and distortion to artwork (especially pixel art). I'd say avoid this for 2D games, while it's usable for 3D games if you want a sharper picture than sharp bilinear and for whatever reason don't want to use LS1 and the like.