I have bought two of them that have both been rendered useless due to lack of updates.

I found out the hard way those boxes have an expiration date. The manufacturers don’t really bother to get the custom boards updated to newer versions of android, so its quite a headache to keep them operational. Theres forums that do custom firmware for them, but ymmv depending on what box you get.

I think it depends which one you take, how open they are for external software. But with Firesticks or cubes you can do 100%. With others it might be worth googling beforehand, if Stremio can be installed on that specific tv box you choose. On those boxes you just need Stremio as an app. The app on your box then syncs with the settings and addons you have in the desktop version, so no hassle.