Everything I do is open source, so all my code is readable by all users. If you don't, see cvwright's answer.
> Also all my editor configs
My editor and shell configs are in /etc. Again, it may not work for everyone, as you may have to share the computer.
> bookmarks, browser logins for Github are all there. If I'd have to switch between users for each project that sounds really cumbersome.
Sorry, I was unclear. I don't logout/login every time I change project. I have a main user, and use sudo to run commands as other users (it even works with graphical apps, provided you whitelist them)