I upgraded from an unlocked 7 pro. I only got the T-Mobile version because they gave me too good of a deal to pass up. Honestly I'm pretty happy with it stock. There's not much you really need root for anymore unless you're developing. It was a big plus back in the day but not so much anymore.
Honestly if a service provider is going to tamper with the device, just don't bother with them.
I'm in the UK but the crap I've seen people have with T-Mobile and Verizon is just insane, avoid them like the plague.
I think you'd be better off converting a Chinese phone and that's something I'd avoid more than sleeping on the opposite side of the bed to amber heard.
Go global, unless theres a fool proof way to make it to global.
EE in the UK did this on the Sony z1, I ended up bricking my device, so I sent it back via a third party retailer.
Original - EE.
Retailer - carphone warehouse.
They sent me an unlocked version, with a normal bootloader.
Not sure if that's an option for you. A little convaluted but certainly worked for me.