Aq salt is for external problems like fin rot.
If your boy is bloated, try fasting him for a day or two, and if he's still bloated, use EPSOM salt.
Dosing and water change requirements are the same for both salts. AQ should only be used for a max of 10 days while epsom salt, if need be, can be used long term.
1 tsp/gal premixed is for general issues. 2 tsp and 3 tsp are used for more serious issues. Water changes are dependent on size of tank you're using.
AQ salt isn't safe to use with live plants and is easier to treat in qt where you can do 100% water changes daily.
Epsom salt is ok to use with live plants so long as you don't over dose on each specific plant's tolerable range. It's also easier to treat with in qt with 100% water changes every day. If long term use is needed, you can treat your tank with the correct premixed amount and just do more frequent, regular water changes.