Juice-specifics become super important once you start sub-ohming. For super-sub-ohming, as in lower than 0.4Ω or so, most people aren't comfortable with more than 20% PG. As in, 80/20 VG/PG. For example, I vape 95/5 VG/PG. As for nicotine, I, personally, could probably vape around 8mg (or 0.8%...