There isn't, for me at least, a "Magic Ohm" that is best for ALL Attys and ALL Cartos with ALL e-Liquids.
But there is a "Magic Watts" range.
Also, even though my Provari can do Anything that I want for All my e-Liquids, I still use an eGo when I'm out and about. So I buy 2.6~2.8 ohm CE2's because they work best on my non-adjustable eGo for most of my e-Liquids.
BTW - What does L,M and H stand for?