They have some effect, the Captain not a lot, the CD some, it's like seeing old friends.
Natalie , ( biased as from UK, in fact England), she is excellent, she can be understated. She will muck in. Some CDs are a bit aloof, you will see her in Cabanas at breakfast clearing trays, or helping cruisers all over the ship, say on embarkation from port, she will be calling the elevators.
Rachel ( by coincidence from England) was excellent, very attentive, didn't muck in, but would pixie dust, if she spoke to a family, you may find a gift in your room, like a plush toy for the children. She then went high up in WDW.
Clayton and Christian were professional CDs ( Christian trained by Rachel). Warm, but came the entertainment route.
Clayton is a darn nice guy lots of fun.
Brent was aloof, separate, his own man.