the ones labeled as unique cant be put in void storage, they take up bag space int he bank, is there any thing else that can be done with them ?
Getting them once for transmog, pretty much it. They are basically a medal for exalted, they don’t do anything special.
so the physical ones can be sold/dropped ? i have a 24 slot bag, that has 22 of them in it 
some others i was able to put in void storage.
Most tabards can be disposed of pretty easily because they can be reobtained pretty easily. A lot of achievement tabards can be gotten by asking the tabard vendor for another one and that vendor also sells rep tabards.
The only ones you shouldn’t destroy are gladiator tabards, TCG tabards, the two argent dawn tabards from the TBC and Wrath launch events or the shadowmourne tabard. Pretty much everything else is easily accessible if you want them again.
Tabards are added to the Transmog collection. You don’t need to keep them.