Seems to me OP has not heard of E-Sim
It must be a US thing as I don't understand these minor suitableness on low band and Volt or a few niche things some US carriers have but 2 phones and multiple E-Sim especially for testing seems a solution
When I lived in US we just bought unlocked phones outright
I know some users note differences in cell reception but it there really that much difference in DL speed etc that it warrants 4 purchases, when E-Sim can get you around many issues
I could care less about e sim when I have the money to do what I want but thanks