18mg 70/30.
That's a very popular strength and ratio (well, in the UK, anyway).
How many different brands have you tried? Some liquids are harsher than others. I just filled up an atomizer with 11mg Hangsen and it's as harsh as anything. (that was the plan). I also have some others that are barely hitting, even on a high power device.
PG is harsher than VG. Mystic Juice - Royal Vapor (60% VG) is very smooth, almost too smooth really.