I don't know where the repeaters are in the building, what they look like, who makes them, or anything other than they work for Sprint, Verizon, and AT&T. I get a consistent -90dBMish EV-DO signal inside.
I work in an EMI Proof building. It's basically a giant Farraday cage. As soon as you walk in the door, the cell coverage drops out. Some years ago, before LTE was a thing, they installed cell repeaters. Would these older repeaters be able to pass LTE, or will I be stuck on EV-DO at work?
PRLs are irrelevant.
The only reason you should need to change PRLs is if you want to roam on Verizon 3G, which requires placing a Verizon PRL on your device.
Other than that, don't worry about PRL.
I disagree. I bought my Epic because it was the best phone I could get, even though I don't get WiMAX locally. The Samsung Transform would be what I would have been stuck with had I bought my device based on connectivity alone, and I think that the Epic was the clear winner there.