I got the UK version of the 15 PM last year while visiting London.
I had the same concerns about less cellular bands vs the physical sim card tray but honestly, I haven't noticed much a difference speed or coverage wise since bringing the phone back to the US.
The only thing to keep in mind is while it's already unlocked for esim capability on T-Mobile and AT&T, you either have to ironically get physical sim card to use Verizon (or a carrier that uses it like US Mobile, which is what I use) or call and sweet talk Verizon into whitelisting your phone's IMEI number to allow esim use.
I tried to sweet talk Verizon to no avail, they said I had to sign up for a plan, even a prepaid plan first before they could add my phone to their esim database. So I did a semi-sneaky thing where I got a call and text only esim plan for very cheap. It was good enough for the customer service representative who immediately added the IMEI number to their database, and since then my phone has had no issues with US issued esims.
So yes, it's ridiculous Apple has released the third iPhone where the US has made iPhones esim only. It's obviously not a constraint issue since the rest of the world has the sim tray.