I have an old Dell desktop with a GeFirce GT 635 gfx card. It uses nouveau in live iso. Do I need a different driver from Nvidia? I’m guessing yes but not sure which one.
Its code is NVE0/ NV108 as reported in live iso also using inxi -G, so it’s a legacy card.
Should I pick 470-dkms? Should I use this latest one https://www.nvidia.com/download/driverResults.aspx/181159/en-us/ ?
What will get installed if I choose Nvidia drivers in the installer? Will Wayland on KDE work?
It will work on nouveau so you could install EndeavourOS using the default entry in the menu. Then it will be install with nouveau open source drivers. Then you could install the Nvidia 470.xx version drivers from the AUR if you so decide. The legacy cards aren’t supported by the latest drivers so these are the options. Maybe you’ll be satisfied with open source drivers. I don’t know how well they work with this card so you’ll have to see and go from there.
So I shouldn’t choose Nvidia drivers during install? And when do you need dkms vs normal?
How does the Mint driver manager work? I saw a video where it recommends the right driver after detecting the gpu.
If you install official Nvidia drivers then Wayland KDE won’t work. If you don’t intend to play games, don’t install any drivers.
you only use dkms when not using the default kernel. (zen,LTS etc…)
Sorry i missed this part. But @mrvictory has given an answer on that. I don’t know how mint driver manager works but i assume it’s like any other tool that is used to install drivers. This isn’t mint. 
It’s older hardware so as i said above install it with open source and see how it works. If you so decide it’s up to you if you want to try the 470.xx drivers. I just said how they need to be installed. I can’t say how this system will work on either driver or whether it would work on Wayland at all or very well. You’ll just have to try it for your self and see. dkms is used if you are using other kernels as it will build the modules for them so you don’t have to reinstall when there is an updated driver or new kernel. In this case i don’t think they’ll be driver updates much for graphics.
You can check here which Nvidia driver version supports your card. Looks like the 470 series is the latest for that card.
Whether you need an Nvidia driver depends on what you want to do with the machine. Nouveau is good for most everyday easy tasks, and there’s nothing special to do to maintain it, just normal system updates.
If you want to play heavy games, then Nvidia driver is probably needed.
However, Nvidia cards will be outdated because Nvidia will eventually stop updating the driver - then nouveau may be your only choice for the card.
All I want is hw accel, some links I read on the arch wiki say the open source driver will work with binary firmware needed in addition. Iwant VAAPI / VDAPU to work, maybe CUDA? In both media players and in browser. I realize this is not as straightforward as in Windows.
I tried looking for a cheap AMD gpu as well, under $25 but didn’t find one.
ArchWiki says neither Firefox nor Chromium support HW video accel with official Nvidia drivers, use nouveau instead.
https://wiki.archlinux.org/title/Hardware_video_acceleration#Application_support