I’ve researched the G7 Power models and it looks like the 64gb variant is not currently compatible with Republic. From what I have found, the XT1955-5 is only the 32gb model (not a 64gb model). I did see a dual-SIM international version on Amazon, but it’s not compatible with Republic right now. Additionally, Motorola’s website only lists the 32gb model for the G7 Power. This would lead me to believe that the 64gb model with 4gb of RAM is an international variant that’s not currently compatible with Republic. Could you point me to the place where you saw a 64gb model along with the XT1955-5 model number?
Regarding the storage, you use that for storing apps, pictures, songs, files, and data. If don’t you use a bunch of apps, don’t download a lot of music, and/or take a ton of photos (that you don’t backup and delete from the phone), you should be fine with 32gb. The G7 Power also has a slot for MicroSD expansion so you can add some more storage should it fill up. If you aren’t a media junky, you should be fine with 32gb.
I hope that helps!