People's experience with unlimited internet plan and the ZTE MF279

I just got a ZTE MF279 internet device and signed up for the monthly 100GB data plan. I am very happy with the service it is providing me and it is so much better then the 3Mbps DSL I have been suffering with for over a decade now. I read about the rural internet plans that offer 250GBs and 500GBs, but I was told that even though I live in a rural area they were not available here. 

We can use a lot of data, since we are cord cutters and steam a lot of video and also have several gamers in the house that download updates and whole games. I'm wondering what my experience might be like if I switch from the 100GB plan and just put the MF279 and all my phones under the unlimited plan. I know my service can be degraded after using 22GB, if there is network congestion. I would like to hear from people who use the unlimited service in rural areas to see how often there service is slowed down after using 22GB and when it is how bad is your download speeds. Any issues with AT&T and using too much data under the unlimited plan?

I would be happy to pay for 500GB plan if they would let me, since that would be perfect for my home. Since I can't I am trying to decide if I should stick with the 100GB plan or switch to the unlimited. As a cord cutter the discount they are offering on DirecTV Now with free HBO on the unlimited would be an extra benefit we would use regularly. So I am weighing that in as well.