If I’m understanding you correctly, I believe you are referring to the function signatures. Those are just there to help give you type/argument hints. You don’t actually need to select those definition, just the function itself.

As for the 2nd piece, it might be because you don’t have floating windows enabled. If you are using a recent build of Neovim + coc.nvim with floating window support, you should be able to see it. Check out the FAQ to see if anything there helps you out.