He had worse potential than Luffy from the beginning. Luffy was much stronger than Ace at the same age. That should tell you elready the gulf in talent between them. Even with an OP devil fruit, Ace still sucked.
His Willpower was small, that is what it takes to get to the top.
Yes, he used barrier haki on Kaido in chapter 1026 against dragon kaido. He learned both barrier and internal destrcution from hyougoro in udon. He also used barrier haki+ internal destruciton haki on his newer version of king kogn gun in chapter 955.
That FS is what allows Luffy to dodge majority of Kiado's thunder bugua at point blank range. It also allowed Base Luffy to fight hybrid kaido 1 v 1 as shown in chapter 1009, before he even got coating. FS is that OP. It also allows Luffy to handle any opponent. Hax people like Law and Sugar.
That was against a weaker kaido that struggled with moriah and did not have his hybrid form and next level sky splitting CoC yet. Oden fought a weaker Kaido and got one shot from an unamed Kaido club attack, with 1 hand.
Kaido even used 2 hands to attack Luffy. Not just that but Luffy has not...
Current Luffy is above Oden already. He surpassed Oden in chapter 1010. Zoro will surpass Oden at the end of this Arc, when he heals from defeating king. Zoro will be 20% above Oden.
kaido is stronger now then he was back then. Current base Luffy split the sky with Hybrid Kaido. Oden did not...
For the no touching technique, you need Advanced armament Haki Barrier and CoC Caoting together. The reason Luffy's attacks are so devastaing is because he used Adv CoC and Barrier + internal Destruction to injure kaido signicantly.
Big mom does not have internal destruction haki, it is the same reason Yamato also could not take off her cuffs. She had no internal destruction haki.
That haki is very rare. Only Garp, Luffy, Shanks, Roger and Rayleigh have it.
Luffy, Luffy had 3 Gear 4 modes and 3 haki, as well as Oda stating Luffy was the strongest Strawhat in the databook and Luffy's feats as well support this.
All this means is like I said before Luffy was just straight up stronger than Zoro, despite him having barrier haki.
Asura had advanced...