It's only got 1GB of RAM and 8GB of storage, and reviewers indicate that there's some bloatware on it, but it's got Android Marshmallow (ver. 6.0.1) so if you use it with a WiFi connection and don't install much else, other than the CellNUVO app, it should work well for you.
It will work but I'd go for something a little better with 2gb ram. 1gb is pushing it in my opinion and a better phone will save you some frustration down the road if they ever beef up the app and make it more resource hungry.
There are quite a few model released by umidigi on amazon that look good. They have the one max which was $180 but you are better off with...
The F1 is particularly interesting for $220. Looks like a Oneplus 6t with a big battery, big 1080p screen, headphone jack and decent mid range processor 4gb ram. Dual sim. Even has verizon band 13 and cdma though whether it works on verizon is unknown. Only really flaw is that the cameras aren't that good per the reviews but will suffice. I would never have expected umidigi to have good cameras anyway.
Personally I think the s3 pro is getting too expensive for a budget manufacturer and you will notice some compromises in the $300-400 price range vs other phones. If you are willing to risk indiegogo and waiting months for the phone then the price is probably good right now at $269. No way I'd pay $385 for it.
Republic Wireless 2 mo of service for porting in...
"The promotion is compatible with Republic Wireless' $15 per month plan that includes unlimited talk and text with 1GB of data ($5) per month. The total value of the discount is $40."
This would be awesome for someone like me who lives in a Sprint deadspot (I assume the software would realize poor voice service and go VOIP to get me better service).