I tend to go with high VG for the vapor production, but it definitely causes wicking problems in my 510 carts. PG, on the other hand, seems more prone to leaking. I probably do about 40% VG now. You might shoot for 20-30%, from what I've read on this forum.
I have the same problem with supplies that don't list PG/VG content on the labels. I gather that over time we'll be able to make reasonable guesses by the viscosity of the liquid, PG being thinner. But I'm not quite there yet.