My issue when I looked into this is that, because of DRM (yay), you cannot easily get full HD video on commodity hardware. For example those Konstakang Android TV Raspberry Pi builds will only get Widevine Level 3, which limits you to 480 or 720p on apps like Netflix.
I ended up going with a full Windows Intel N100 mini-PC. Windows because the only way to get 4K Netflix is to either use the Windows app, or Microsoft Edge on Windows. [0] Any Linux would limit me to 720p. And even then others like Max do not support 4K on Windows [1]. I believe Disney+ is the same.
Another choice I wasn't aware of when I got my hardware is Kodi running as an app on an official Android box with Widevine Level 1. Kodi is able to use Android's Winevine allowing for full quality 4K playback through plugins for Netflix [2], Max [3], Disney+ [4]. It leaves you reliant on these (open-source) plugin rather than official apps for all the good and bad.