You would start with the models that work with your carrier. But just because the bands are supported doesn't mean the band is enabled on the tower near you. I'm just someone that worked in base station design long ago.
But you can narrow it down with the models you can buy. I've seen folk do such research only to find a model that is not available.
Hello I'm trying to find a 4g lte mobile router that is capable of manually selecting cell frequency bands. The cell tower I'm connected to has 850mhz (band 5) and 1900mhz (band 2). Band 5 is just so congested and unusable. I would like to use Band 2. My Galaxy S7 can do it in service mode but I would like to get a lte router with the same option with Ethernet ports as well