Vergo cracked Sanji leg without even using hardening. Sanji acknowledged he would have lost the fight.
Fake, we can't tell that for sure because his "full body haki" mode also doesn't show his legs coated like it does on the torso. I believe he did used Haki (at least we can 100% confirm they had Haki clashes due to the sparks the impact of their legs colliding were making for most of the exchange)
And yeah boundman is around or above YC3, no wonder he beat Doflamingo. The biggest disadvantage was the exhaustion due to the amount of Haki usage which would make him useless.
See: During EL, Gear 2 wasn't enough to beat Lucci by itself. Zoro and Sanji mid diffed their foes once they used their secret moves, while Luffy left his fight without being able to move and with much more difficulty, which makes sense given Lucci had almost twice as higher Doriki was Kaku and Jabra.
Now listen: Sanji almost break Blueno's tekkai in their first meeting, Luffy beat him with Gear 2, the math tells Zoro and Sanji were already competing with Gear 2 the moment Gear 2 became a thing, otherwise they would have no chance against Kaku or Jabra. Which means, once Boundman became a thing, Zoro and Sanji were not as far in power to Luffy as you might think