Description
This gives you a single box where you can enter tokens to form the default username.
It seems to work, but in D7 the patterns section ("Only use the below pattern elements") was empty. This is supposedly because there's a dependency on the 'profile' module, except profile doesn't exist in D7 (I tried profile2 instead but it made no difference) and profile2 doesn't exist in D8.
auto_username displays tokens OK and is more powerful / has more settings including customise at what point names are truncated, etc.