[jprgomet]

You need to buy an Apple TV 4K if you want frame rate matching with virtually all video streaming Apps like Netflix and Amazon Video for nice smooth video playback. This really works well and I highly recommend it. Killer feature IMHO.
No idea about HBO if it's even avail. on ATV 4K.
MrMC (Kodi Jarvis fork) or the really simple Infuse App is used for local content video playback.
Downside - you have to use home networked storage like a NAS, home router / Hard drive file server or even a cheap LibreELEC machine would do with its inbuilt plug n play SAMBA file server.

You cannot plug a USB HDD into an ATV 4K.

You will have to manually switch the Android resolution settings to match/guess the fps of source video content on the Mi Box. Even then it may not work properly. Welcome to PITA world. Not recommended for what you want a media player to do.
Kodi cannot do auto refresh switching on the Mi Box either.

 thanks on fast reply .. so I guess Apple TV it is .. streaming will run as expected and other online services .. I will get correct frame rate .. 
I have R7800 Netgear router that has samba .. maybe that would work ?

I remember problems with subtitiles in separate file over network .. will I be able to get subtitles when pulling mkv + srt over network in "kodi" app or Infuse?

Looked up the price of apple tv .. 200 eur! .. a lot! .. is it really worth it?