I use wrist wraps (not straps) on DB rows for two reasons: grip and owies. If you make a fist and wrap a wrist wrap super tight, it locks the tendons down and helps you keep your grip closed. This helps me in high rep work.
Second, the dumbbells I use at my gym, even if I hold them with a super tight grip, rub against the skin of my wrist and rub holes in me. Ouch. The wrist wrap takes the rub out. I don't know about using them for crushers, unless the angle makes your wrists hurt.
I don't use elbow sleeves, but I'm of the opinion that if something makes lifting better and less painful for you, and that something is legal, or doesn't negatively impact your goals (e.g., you shouldn't wear a shirt all the time to protect your shoulders if you are trying to strengthen your pecs!), then go for it. As I get older, I'm always happy to find things that make me hurt less.