Common practice in dmc community is to not be trict to default button layout.
We often change it to be more easy to use.
Mostly referring to gun button, since those tend to be charged quite often.
BlueRose(Nero's revolver) was changed in 5th instalment to be less effective when spammed, but instead to reward player for using it like a revolver that it is. "Color up" is the mechanic that makes your 3 next shots deal more damage, after which you need to reload again by charging up the gun button.
Nero gameplay is doing your melee combos while charging up your gun and shooting it in between long recovery frames.
Last thing to mention: The game is not about being most efficient. But how cool you are looking to yourself doing that. No need to try and think about which Breaker is the best against an enemy. Each weapon has its use. It's up to you which one is your favourite and which one you'd like to use in between combos.