The boxes all work the same way and you may install all apps on all of them. Differences are in RAM and ROM and the menu. Also many boxes come along with poor remote control. Imho the Xiaomi MI S is top. I'm still using the 1st Generation Box. I don't know the True Box.
Sure. In my case it's also the name of the App. Others are i.e. Wizz or Vavoo. Tukom has lots of shops doing the Setup for you. Tell them what stuff you want to watch and they install it for you, I.e. Netflix.
best Box I ever used. I tried many. For the setup and updates I visit a shop at Tukom. They charge me 100,- thb for the service. That's why I don't want a smart TV.
Currently I'm using IPTV. It's 1500,- per year. I tried Wizz, but that's loaded with 90% Brit stuff.
If you have enough cash, get an Elite Visa. If you don't want to spend that much money or think about a one year stay in Thailand only, i recommend the METV and some border-runs or Visa-runs. 3rd option is the ED visa to study Muay Thai boxing or anything else, but you need to attend the classes.