Autorefresh can lag the server when certain Lua files are edited. This happens when the refreshing cascades. This can be unwanted behaviour when editing the scripts of a large project on a live server.
To disable autorefresh, add -disableluarefresh to parms.
Loading screens are added by defining a website with sv_loadingurl, which is in gmodserver.cfg by default. This file overrides other files.
Links should not have http:// or an ending/ .
Gamemode is changed by editing start parameters in the LinuxGSM config file.
Other gamemodes like Zombie Survival can be found on the steam workshop.