I used 12 ga OFC by Monoprice. But really any OFC will work 12-16ga.
I don’t have a photo of the board layout, but would be happy to look over yours or even walk you through it via email or PM/DM if you need it.
I did use sound deadener. In mine, I used some broken up rockwool. This was more to do with breaking up standing waves than anything else. The stuff I linked will work just fine. I used what I had on hand.
The weight specified is per passive radiator. So X grams on each passive radiator, like you said above.
