Only crafted and some barter sets can be transformed. I know for certain that IC sets are convertible as I converted a entire shield breaker set to imperial, dunno about others, but I bet there are more.
Sometimes, I dream about...cheese...
Dermont - v16 Pompous Altmer Sorcerer (With a very arrogant face!) Egonieser - v16 Nord Stamina Dragonborn Wannabe Endoly - v16 Tiny Redguard Sharpened MaceBlade Egosalina - v16 Breton Cheesus Beam Specialist Egowen - v16 Dunmer Whipping Expert (Riding crops eluded her)
(Yes, I had to grind all these to v16) Akamanakh - lvl 22 Khajiit GankBlade (Inspired by Top Cat) Targos Icewind - lvl 34 Imperial (Future) Jabplar
(CP 830+)
It's far too limited though, converting crafted sets isn't going to cut it. Ideally we'd get the option to transform any set piece into any style we know or at the very least into the style of our own race.
PAWS (Positively Against Wrip-off Stuff) - Say No to Crown Crates!. PC EU/PC NA roleplayer and solo PvE quester