I’ve been on US Mobile for several years. You can choose between the Verizon, T-Mobile or AT&T networks. I’m on the Verizon SIM. Yes, you are deprioritized. No, it’s not an issue.

I’ve been very impressed with US Mobile’s support, though I’ve only needed it a couple times.

Pretty sure mine was attached to the paperwork when I got my non-provisional drivers license at 18.

Are you me? You said it much better than I could.