I currently use an Nvidia Shield as my Google TV. I used to have the original 4k Google TV and had issues when upgrading to the Google TV streamer. The Nvidia shield is old - but it's still the GOAT.
This is an alternative YouTube app and it's fantastic.
Some features I like:
Be careful downloading it though - make sure you get it from a trusted place.
This is a media center like Plex or Kodi that allows you to stream your own media. It also lets you set up a DVR for live television or IPTV channels.
Moonlight is a game streaming client that you can set up to stream games from your PC on your local network. I run Steam in Gamescope and use Sunshine to stream it to my Nvidia Shield. I connect an Xbox controller to the shield with bluetooth and I get to have the full console experience.
The default Google TV launcher has ads on it. Projectivy launcher doesn't.