Coil resistance below 1 ohm. Lower resistance lets more current flow, which means more heat, more vapour and stronger flavour saturation. The trade-offs are liquid consumption and battery drain, both roughly double what a pod kit uses.
High-VG shortfills at 70VG or above, in low nicotine (0 to 6mg freebase). Thin 50/50 liquid floods and spits in big coils, and 20mg salt through a sub-ohm coil is genuinely unpleasant; the formats exist for different hardware.
If the mod has a 510 connector, yes, physically. The real question is power: check your coil’s printed wattage range against what the mod can deliver comfortably. A 200W dual-battery mod loafs along with any tank here; a 40W single-battery device will limit which coils you can enjoy.