MediaCodec in Mi Box does not support deinterlacing. It works in discard (single field) mode - display one of the half-pictures, discard the other. Also Mi Box does not support AFR and HDMI CEC. Best android tv box for IPTV - Nvidia Shield TV.
Op what VPN you using? Assuming your UK? Bc they're funny with vadder. Most countries VPN not needed for Vader. My friend in UK using Vader rocking ExpressVPN with smooth results. Use kodi linked with Vader better experience as well.
The Shield has been the best box since 2015 and still is. This is more or less a testament on how shoddy all the other boxes are.
BuzzTV XPL3000 is a decent choice for the android experience with iptv, ofcourse there is the Nvidia Shield if you want to go that way as well
For just streaming, Mi Box works great.