Just figured out this is a waste of time. US Mobile and Verizon lock the eSim to the emei while T-Mobile only uses it to see that you have a capable phone, like Red Pocket does with physical sims (although RP does keep track of what phone you are using it on with the emei.) So @Trip was right in this case on liking physical sims.
Verizon has a reputation for being frugal with MVNOs. After looking around, I also decided US Mobile was my best option. People have gotten C band on it. Hoping for esim for my S21 Ultra. No luck so far. Red Pocket does not claim Verizon 5g, although they say Soon!(TM). I do see some 5g with it.
Typically MVNOs are deprioritized, thus I am reluctant to claim truly getting top speeds with one.
Did some exploring yesterday/last night and didn't find a shred of C-Band, including with my brand new US Mobile SIM. Did find 4CA CBRS but the site seemed backhaul constrained; both that plus 15x15 B2 and band-locked 2/66 got me 190 Mbps or so.
Did some more exploring yesterday/last night and I think I spotted some LAA downtown but didn't get a chance to confirm before it went away in favor of mmW, which also went away pretty quickly.
Also saw another n66 site, as well as an n2 site, making AT&T the second carrier to run n2 DSS within a few miles of me.
I think at this point they won't be able to advertise anything flashy, but due to the sheer amount of CA they're throwing at customers here they can keep their network at 50+ Mbps until they can deploy both 3.45 and 3.7, and that's probably enough.