My C. isosceles has maxxed out at about 4" long. He's not aggressive towards any other tankmates. He eats as well as anything; I never had trouble feeding him LRS, mysis cubes, Ova, PE pellets, NLS pellets...
If anything he will defer to others (anthias, the bigger wrasses), but he does not go without food.
He's very active in the water column and fun to watch swim.
I do not have experience with Rose-Banded...as I suspect you know, it is in the same group as the isosceles but is rarely available (from my limited experience).
Hopefully Hunter chimes in on this thread...