Need Explanation 1080p (Pass-thru only)

I just installed my first Tivo. Generally, I've been able to figure things out. However, I do have some video resolution questions.

1. The following are checked: 480i, 480p, 720p, 1080i, 1080p (60 fps), 1080p (pass-thru only). Should I leave them all checked? (I understand why 2160p (60fps) and 2160p are not supported).
2. What does "Press UP while watching video to switch output formats." achieve? While it demonstrate the best Tivo/TV compatibility?

Any settings suggestions will be appreciated.

Thanks in advance.