If you’re going with a scaler, it’s definitely worth it to invest in better cables (even though the n64 uses the same connector as snes, it does not support rgb without mods)
https://insurrectionindustries.com/product/nintendo-s-video/
https://insurrectionindustries.com/product/sony-playstation-rgb-scart-cable/
https://insurrectionindustries.com/product/super-nintendo-entertainment-system-rgb-scart-cable/
https://www.amazon.com/HD-Retrovision-Premium-YPbPr-Component/dp/B07TL6L7MY
Some helpful videos: https://youtu.be/VYkWtkvhS9c https://youtu.be/fi7csYj00BU
Also if you’re not too attached to using original hardware, you might want to take a look at getting a mister to play ps1 and before systems (the new super station is a good choice https://retroremake.co/pages/superstationᵒⁿᵉ )
I would say “probably”. A lot of TVs don’t have great scaling from 240p, 480p, and 480i content so a dedicated scaler will look better in most cases. Also be aware that the Ossc Pro does need an additional add-on for S-video (which for an unmodified N64 is its best output).
Upscaler is the correct term. If you are looking for the best possible image to recreate a CRT, the retrotink 4k is the best option. It will require a good TV though, something like a LG C4. The reason being to get good looking scanlines, you need 4k, 120hz, and vrr.
The retrotink 4k also supports all your inputs (Xbox 360 HDMI, n64 s-video, snes rgb, PS2 component, etc…).
Here is a good video why the 120hz is important for recreating the crt feel (a little old and retrotink 4k has only gotten better since then) https://youtu.be/3ZmPkozY6Cg
You other options for a good scaler are the Morph 4K and the ossc pro. This spreadsheet has a good in depth comparison between all three https://docs.google.com/spreadsheets/d/16FBPBD3A1vN_khznTUO1bGrb3LxTIQXfwWfusPeNSsw/edit?usp=drivesdk
I go through different switchers to various inputs of the retrotink4k. I avoid composite to keep it simple and get a better picture.
No problem. The S-video with the N64 should look better with the 2x pro but it might not be the best choice for the PS2. A lot of the PS2 library is 480i, which the 2x supports but it uses Bob deinterlacing. The GBScontrol is the best budget option since you can use motion adaptive deinterlacing (it does not support composite or S-video) I have seen some people recommend this pre built version. https://www.aliexpress.us/item/3256804850466089.html