What I've done is to install X-plore on my TV.
I am using a Google Drive (Now called "Backup and Sync from Google") on my laptop. I can download any apk that I want to try on the TV to a folder in my G-Drive.
Now, If I want to install anything, watch a movie, play MP3s or whatever, I just copy them to a folder on my shared g-drive folder on my laptop, wait for the files to sync to the cloud and then I open the folder on my TV with X-plore and click the file. Easy as that.
Many apps are not compatible with Android TV and they will usually start rotated (although I have previously used an app to rotate my phone screen after I dropped it in the pool and the autorotate stopped working, so I guess that might be one solution), some will only work with a mouse and some won't start at all, like Netflix, which tells me that it is not compatible.
If I want to watch anything on Netflix, I just view it on my phone and cast to the TV. The quality is pretty good.