There's no adminlogin command in Unreal1, you have to setup your password in the player settings menu and then rejoin the server. (once you join, you will be automaticly logged in)
Beware: If you don't remove your pass when on other servers, other admins can see your password.
To remove bots type: Admin Killall Bots
I don't know of a way to vary the number of bots based on the number of people in the game, depending on which gametype your running..there might be some mods that do this. (UTeamFix does that I think? It's got lots of improvements on the bots)
And the no-autoswitch can't be setup as default unfortunatly
You'll have to just use the keybind.