On both of my Hopper 3 receivers you can set the video resolution under TV settings.
The 4 choices are:
480i
480p
720p
4K, 1080p, or 1080i
If you select 4K, 1080p, or 1080i your Hopper3 will automatically pick the correct resolution based on the content as Bobby has said.
I don’t own a Hopper...