is changing username on steam even possible at the moment?

One thing on the profile name: Steam keeps a list of your previous names and anyone can see it from your profile. If you're changing it to get away from an old one, there's a clear name history option in the dropdown next to your name. Your custom profile URL is a separate setting too, so change that if it still has the old name in it.

Depends which name you mean. Profile name, the one friends see, change it whenever you want from Edit Profile. Account name, the one you log in with, can't be changed at all. Only way around that is a new account.