Hello, I have these wall brackets and I really like them. They are very easy to mount and screw well to the wall. The boxes are clamped by 2 corner bars with rubber. The mass of your studio speakers would not be a problem.
As far as sound transmission is concerned, I am not a professional. This wall bracket is screwed to the wall and the speakers are clamped. So there may well be sound transmission. But I think that's always the case when you make contact with a speaker and another object. It also happens when there is no direct contact.