Re: Charm level scaling

There's not an "intended" order that I'm aware of, but I normally do Feros -> Therum -> Noveria -> Virmire, and I only do Virmire after having completed all the side missions that I want to.

The scaling has no direct impacts outside of leveling up and skill points, though it may have an indirect impact if for example you're 1 skill point short of a Charm/Renegade threshold and you would have acquired that skill point from an intervening level up on Classic scaling.