Yup. Tried Kodi. Not sure I like running a broken version of the Fire TV. I don't watch much outside of prime, Netflix, and hulu. Now I do have a ton of torrented movies and the standard codecs for a fire TV are kinda meagre, and transcoding everything again is a pain. For that I liked Kodi. But anymore I just stream from my PC to the Fire TV to avoid the hassle. I dislike paying for HBO go when it is just for one show, game of thrones.
Chromecast is mainly for streaming I assume, I don't use one.
Android TV is a full blown Android OS in a box. Anything you can do with an Android device, you can do with an Android box. I have bluetooth/USB controllers hooked up to mine as well so my kid can play NES games and Android games. It is a FULL OS, not some stripped down software like Chromecast.