We are in the same boat. We use prepaid via Net10 and had decent service for years. Because of this we use the same phones for years. My wife got an iPhone 5 from a friend I used an iPhone 4 until my work required a newer phone to run its apps. I got a free Samsung Galaxy S4 from a friend that got the boot load loop bug, So I got an LG G4 it now has issues and needs to be replaced (all sorts of issues). So now we both need new phones. The wife wants an unlocked iPhone 8 and I trying to decide if I want the same or get a Android phone.
The issue with android phones is they seem to last about two years before they start having issues. I can't afford to spend 800+ bucks on a new phone every two years.
The phones you have listed are the ones I have been drooling over for the last few months. They are all great phones. I really like the specs on the Galaxy S9 and the Huawei Mate 10 has good potential as well.
The research I found on the OnePlus 5 is it made not work on US cell towers as well as they would over seas.