I have a couple vape pen batteries with variable temp control (from 3.3v to 4.8v). Useing the vape cartridges from Surterra, What is best setting for a great tug without boiling the concentrate or getting mouth full of residue?

I would check with them, the staff is very knowledgeable and helpful. As for most, the lower setting will make it last longer. I really enjoy their disposable ones, easy to use and toss when you're done

I don't have a perfect answer but on 1 of mine I have a the ability to adjust the drag by twisting on the mouth piece. And I do know that different blends require different temps.