I got the nvidia shield 2019 and so far it works fast and well and generally happy with it. The only drawback is that the machine itself is pretty locked down as far as adding apps that aren't in the store etc. I don't want some cheap knockoff box android box thats sluggish and never updated. A polished one that works as well as the shield. One that lets me add apks as i wish and access the full app store. I know you can sideload but on the shield its a pain and need to deal with app compatibility issues,etc. I figure I'd get a regular android box to supplement it
What you are asking for doesn't exist. You can either use proper AndroidTV or some cheap knockoff, these are your two options.
Also under the hood AndroidTV is more or less normal Android with an optimized user interface.