I'm only asking because im on an AT&T model, but eventually want to flash T-Mobile roms once our bootloader is unlocked for wifi calling.
It would require some tweaking, but in the base idea, yes, they're all the same (with different radios and likely different kernels). You'll want to just wait a little bit and have devs port to the other models. However, your goal of getting wifi calling likely won't work. Maybe I've been out of the loop, but last I checked the app registers your phone number with the T-Mobile network so it knows where to forward calls/texts to. So it more than likely won't work for AT&T/Verizon. I believe Sprint has it now, but same method.