Many factors are at play with how light or soft a vape is.
1) Biggest Nicotine Content - This is listed in one of two ways on the bottle by Milligrams per milliliter (example 12mg) or by percentage of volume (example 1.2%) both are the same here as 12mg
2) Base mixture - This is listed as a ratio of Propylene Glycol (PG) and Vegetable Glycerin (VG), higher PG content in a liquid will cause a higher throat hit, example a 70PG/30VG liquid will have more throat hit compared to a 30PG/70VG liquid, higher PG liquids will be quite watery where higher VG liquids will be more syrupy
3) Power output of your
device - this has many variables involved, but the relationship between your coil resistance and voltage output will give an integer of power output as watts, though just watts listed will give us an idea of your vapor output, but if you are on a Variable voltage or set voltage
device, letting us know what device and attachment along with coil resistance and voltage setting on a variable device lets us help you better. Higher ending wattage means more heat, more heat means more liquid vaporizing, more liquid consumed more nicotine is delivered. 9mg liquid at 20watts will deliver more nicotine per volume compared to an 18mg liquid at 12watts.