I know this is an obvious question, but I went through the documentation paage and FAQ, and couldn't find an understandable description of what is the difference. I would really appreciate a clarification here.
I'm not a programmer or anything, I just enjoy playing games. Should I use the version with full addon support when I play single player games? What is the difference? Do the shaders work better in terms of visuals or performance?
If you want to use any ReShade add-ons and play a single player game, use the build with full add-on support. If not, use the normal build. If you haven't installed any add-ons, then you are not using any, so the normal build is the way to go. Either way does not affect how the ReShade post-processing effects look like.
The normal build is also allowed by several anti-cheat providers, whereas the build with add-on support is definetely not (add-ons can be anything, including cheats), hence why you should always use the normal build in multiplayer games.