Vulpera, pandaren or mag’har orc?
None, if ur looking for best animations/mog on horde just play belf or undead
I agree with the other guy. Transmog looks like total garbage on vulpera and pandas. I don’t know about orcs.
But play blood elf or undead if you care about aesthetic.
If you’re dead set on sticking to those three races, Mag’har for sure. Most transmogs look like garbage on panda and vulpera.
Just unfortunate that as a mag’har the pet racial is just… worthless for you. Zandalari look badass in most leather, as do any flavor of orc.
Blood elves are just so … bleh. The horde have the undead and the blood elves are STILL the humans of the horde, so numerous.
Of those three, transmogs look best on mag’har. However, mag’har are large and bulky and don’t fit the rogue vibe as well as undead. 
I only wish undead were as cool as they used to be, before 6.0. They had the absolute best, untouchable animations and aesthetic. Now they do not look as cool. More goofy. But if you put a helmet on, it’s not so bad.
Mail is the only armor class that looks good for vulpera
They changed the animations for sure, I dont know if I would go this far. But I kinda would like the old animations back.
I have a strong bias for Orcs.
Snikrot forever.