Impersonating a TL0 user is an option, though personally I find impersonating and having to log back in again as me a bit of a faff.
I like to use a couple of different browsers so I can stay logged in as admin in one and have the new user in the other. I tend to create mine as and when I need them (and delete any I no longer use). To make it slightly easier, I activate them from their admin page rather than following the email links as I don’t really need to validate their email address. This cuts it done a couple of fields on the create account modal and I’m pretty much set up and ready to go. 
Also, having a fresh one each time captures the onboarding messages, new user tips, etc if I’m looking for a ‘whole of onboarding’ experience, versus ‘what does a non-staff account see’.