The answer to all your questions is; it depends. Do you work from home, do you stream content? How important is coverage, are your TV smart TV's?
A cell phone hot spot can be used to do work etc, but typically people who work remote and stream a lot of content; end up getting a dedicated hot spot. A dedicated Hot Spot is stronger, farther reach and has better battery management.
If you stream content on your TVs, they will either need to be smart TV's with a built in wifi receiver, or you will need a firestick or Roku.
Whatever your methods of consuming content, if you are consuming more than a few gigs, you will want an unlimited plan. Otherwise, overages will break you.
Do some shopping around. There are a lot of youtube videos on good plans for RVer's. I was looking hard at Calyx institute.