Double width studs for isolation?

Good best for isolation is to STAGGER the studs. also, most code is 16" on center. There are various products to weave Between the studs as damper. DO NOT use styrofoam. It is toxic as hell when it burns, and probably against code. The products I have seen are Very heavy plastic.....I have no idea how they do it, but this stuff is pretty heavy, providing mass while meeting burn/self extinguising requirements.
By staggering, you DeCouple the walls 'sharing' the studs.
Just looking up, Elvick calls it 'insane'......Nope, just 'sound' engineering. pun intended.

Elevick, You completely misunderstood my post.
by 'stagger' I mean that there are 2 sets of studs, not studs at random intervals. Both sides of a dividing wall are NOT attached back to back on the same set of studs. This will couple them 100%.
Instead: try building 2 half-walls back to back. Total thickness should be maybe 6" using 2x4 studs. 1 set is covered by sheetrock facing room 'A'. A second set of studs *between* the first set and offset about 2" are used for the 2nd wall, being room 'B'. Weave a dense sound insulation/damper BETWEEN the 2 sets of offset studs.
The 2 walls are now decoupled..bass and have insulation between them...for HF.
BOTH walls will be 16"oncenter, but offset 8"......
Man, I wish I could attach a simple drawing!