Check the coverage maps of the big three and see who has best coverage where you live and work. (ATT, Verizon, T-Mobile)
I think if you BYOD you can get something without a contract. You can buy a refurbished 2 generation old phone on eBay for two hundred.
There are discount carriers but they piggyback on the big carriers and are probably not worth the trouble.
In the US it is legal (for some insane reason) to lie about “unlimited” so read the fine print. Get an “unlimited plan” that meets your needs and don’t worry too much about it. I’d get one where they don’t charge extra for hotspot.