Katakuri was literally a last minute character that Oda used to give Luffy a power up. I've been saying this ever since I saw Oda retconning his DF, and had no idea what his DF was.
This was the original Katakuri:
User of the "Powder Powder no Mi" and a swordsman.
Oda knew Luffy needed a few power ups to beat Kaido, so he made up a character with FS so Luffy could copy him.
Like I've been saying for years, Katakuri/Cracker are just Blueno/Rob Lucci of the New World. The only difference is Oda gave Luffy the power up at the end of the arc in WCI.