I vape 25mg salt nic in "MTL" tanks, usually at 7-11W, 15-20W on sub-ohm coils. I don't do too much MTL. I take 3-9 second DTL "tokes". I like cool, smooth vapor.
Salt nicotine is just nicotine that has been extracted using a method developed in the 90's in China. It's also odorless and tasteless just like freebase nicotine. Freebase nicotine, however, is a colorless liquid, and salt nicotine is a crystal (hence "salt") that has a slight amber color, which is still noticeable even after being diluted to 25 mg/ml.
I use it because it's less harsh. 25mg salt nic solution is mellower than even 10mg freebase. IMO. YMMV.