Salt nicotine is smoother at higher strengths and works best in low-power pod devices. Freebase is sharper, slower to absorb, and shines in sub-ohm mods at 0–6mg.
Match the liquid to the coil: 1.0Ω and above for salts, below 0.6Ω for freebase. Never put high-strength salt in a high-wattage mod.