Hey Wally!
So know one gets mad, a lot of this is just repeating things that have been written earlier this season in different threads. So it's a little like plagiarism, I suppose, but it answers your questions. Credit to all those that put these thoughts together previously.
Deadheading: If you do not cross your plants to collect the seeds, to me it seems wise to deadhead. Otherwise your plant can expend energy on growing bee pods that you don't even want and don't really look that nice. In reality, I think deadheading is more cosmetic than helpful to your plant. And some people live head. So instead of going around first thing in the morning to pinch off the wet, spent blooms, go around at dusk and do it while they are still actual blooms. It's much more pleasant than dealing with mush mummies. I collect seeds, so I don't deadhead so much. Not many things sting as much as removing a spent bloom for a picture, and then remembering you crossed that bloom for seeds the day before.
Cutting back scapes: Again, if you don't collect seeds, as soon as your blooms are done, you can cut them off down by the ground. Don't be too aggressive and dig into the dirt or you can harm the crown. If the scapes are completely brown, you can just pull them. If they are still green, even just at the bottom, it's better to cut them or risk damaging your plant. Your scapes will stay green as long as there are developing seed pods or prolifs. If you don't care about seed pods or prolifs, cut them down at will.
Foliage: Theoretically, if it's green, it's generating energy that your plant can use for root growth in the fall or store for a better spring. You are always welcome to pull or trim off brown leaves and tips. I read a book by Tracy DiSabato-Aust that refers to this as deadleafing, and the maintenance step that happens after all the deadheading. Your question was, does you plant benefit by cutting it back. Well, it seems your daylilies are better off keeping all the green leaves they can. However, Tracy does realize sometimes the leaf deterioration can be bad or some people don't have time to deadleaf the rest of the year. So she does give advice if you want to cut back your leaves. She suggests if you see new leaf growth you can cut back to there, or just cutting it all the way down to 3 inches above the ground. She says it will take several weeks to a month to get new foliage to replace what you cut if you cut it low. I guess that means you need to do this at least a month before you expect frost. Tracy suggests just using hedge sheers for cutting foliage.
Tracy's book that I paraphrase is "The Well-Tended Perennial Garden", for reference.
