Larger charging handle latches can be nice when you have optics on the rifle. They can get too large and snag at the wrong time. I like the medium size PRI Gas Buster
A phosphate BCG with chrome bore is the mil-spec. Coated BCG's may reduce cleaning time a little, look pretty and feel good. If you feel they are worth the extra cost, then go for it. All deployed US military rifles use phosphate BCG's.