So I'm getting the impression here that not everyone is a Starlink user, nor do they have a desire to become one. I see that others are curious but may or may not have all the info needed to make a decision.
Let's keep in mind that the OP had questions for actual users. Also, I can really appreciate all of those who have tried to explain some of the nuances of SL billing and variety of plans - however, it is not a one size fits all uses sort of thing. I can explain why I have it, how I use it and how I'm billed for it but I cannot assume that will match everyone's need. I'm not a techy person so I'll just do my best and do what I can.
To the OP - I bought the Standard dish (some refer to it as Gen 3) and not the Mini. In the Mini the dish and router are built together. The Standard allows the dish to be deployed a distance while keeping the router close to the camper and thereby centralizing the internet signal. Given that I travel widely, I wanted to be able to get the dish out from under trees, if needed, but maximize my signal from the router.
The dish choice and plan choice are 2 different things. One is designed, but not limited, to be paired with another. I started out by choosing the Residential Plan: $165 per month of unlimited data. This was because there was a deal on the dish at the time requiring the Res Plan. I did not know how much data I'd be using anyway since I was accustomed to my unlimited home internet. Everyone's needs are different, of course. I changed my address every time I moved camp, doing the change before I packed up so it would be updated by the time I relocated. I never got any sort of violation notice from SL. I never used more than 100gb of data, even when binging on movies so those first few billing cycles were pricy. As others said, Res Plan is comparatively expensive to home internet plans. It is reliable internet all across the country, though. For those who travel in areas that have no cell signal, it may well be worth it. For others. it is not.
I changed plans to the Roam 50 plan as soon as I was able. This give you 50gb of data and you can get billed $1 per gig for overages. This means that you can use up to 164 gb of data before deciding if you want to switch the plan back to unlimited Residential for $165. The switch is pro-rated, thereby meaning that you do not owe any more to switch. This is what I do and it may or may not fit your purpose.
Lastly, I asked myself the same question about taking the dish with me from home to the road and back again. Yes, you can. Depending on the plan you've chosen, you may or may not need to update your billing address before you do so SL can "find you". I do not do this because my home is monitored over the internet (heating, alarm, door access, etc) so I have to have home internet. My local service is fairly inexpensive so I leave it alone. When I am home, leave my dish with the camper and powered by solar. I put the SL in "standby mode" and this gives me 5gb of data for $5 - good enough for my purpose. It is my understanding that you can have 2 dishes one 1 account but each needs their own plan; which might not be cost effective. I don't do this so I can't really speak to it.
There is a 'StarLink for RVers and other mobile users' group on FaceBook that I joined. Lots of other groups and forums you can follow, too. I would suggest joining one. The knowledge and experience provided is invaluable.
Good Luck in you decision making and hope to see you on the Road!