Do all vendors have new gear?

nope. every planet vendor has a chance to drop gunsmith guns, though, like usual. so you might get one of those.

planetary vendors dont

tower ones do

(i am not counting amanda holiday)

I believe so I haven't checked all of them but I seen on preview of Sloan on titan she had new stuff

No one is selling new gear only way to change appearance is through ornaments the only new gear is Mercury planet set Raid liar set Ornaments are: all faction , vanguard, cruciable and raid sets