Is it possible to make the propspawn restrictions not affect the admins on my server somehow?
Not unless you're using Uppl (see releases section).
Is it also possible to remove the messages that shows up in chat when I change any settings so only I see that?
Or is it possibly allready like that? 
Not with sbox_ and sv_blah variables. They're controlled by a Source engine message that I'm (95%) sure can't be blocked.
As for any other changes, admin logging of commands, see your /addons/ulx/cfg/server.ini ... if you change any settings there, save it in /gmod/cfg, or it will get overwritten next time you update the addon.
By default, most ULX commands run from game console (instead of the menu) will show (silent) to admins only.
