...at 3.7 volts what cartos are gonna give the best vape.
Nice choice on the roughstack! I have one too and it is spectacular.
Atty/carto choice is largely personal preference, and on what type of juice you're using. At 3.7v, you should be looking for something between 1.7-2.8 ohms.
I typically use attys because I prefer to drip (or dip with a 306), but I've had some nice vapes with Royalsmokers E2 R4 cartos (2.4-2.6 ohms) and CE2 "clearomizers" (also 2.4-2.6 ohms).
Good luck!