When connecting my Acer Predator Helios 300 (144hz panel) to my 60hz TV, there is noticeable "static-y" artifacting, as seen in the picture above. Note that it is always changing, similar to old "TV snow". I'm assuming that the refresh rate difference is the problem here.
While connected to the TV, going to Settings>System>Display>Advanced Display Settings shows Display 1 (laptop screen, listed at 1080p@144hz) and Display 2 (TV, listed at 1080p@60hz). I'm not sure where to go from here, and all searches I did led to people asking about the opposite situation: connecting a 60hz laptop to a 144hz display.