Re: visuals?
Re: A TV show (no matter how lame the story line and acting might be) is a complex interaction of visual, speech and musical clues... remove any "channel" and you're likely going to miss a lot of the action.
Depends on the show (and in particular, the director). If you watch any soap, the drama tends to be in what the characters say rather than do, and the visuals don't actually change much. Certain other TV shows are like that as well. For instance, you can generally get the gist of what is happening in Doctor Who by listening to the dialogue, if not the finer detail. Then there are other shows where the soundtrack is almost secondary to the visuals, and you would have little or no clue regarding what is happening if you weren't watching (e.g. Legends of Tomorrow).