I have seen posts by people with flourishing reef aquariums chock full of the most demanding coral species and they use all sorts of different reef salts. There really is no such thing as a “best“ salt mix. The difference is in the work and knowledge of the reefer.
If you want decent you tube videos, Bulk Reef Supply covers many of the most popular in a series of videos on reef salts.
If by “cleanest”, you mean a salt mix that dissolves without leaving any undissolved residue. BRS says that would be B Ionic. It is a bit clunky to mix up because it is a multi step process: add sodium chloride to the water and let dissolve, add magnesium salts to the water and let dissolve and so forth. For a one step process, tropic Marin pro is nearly as clean and it is dump the salt into the water and mix.
But reefers have enjoyed great results from the Red Sea mixes and Instant Ocean.