So the big take away is that Kizaru apparently defeated Snakeman. Luffy immediately went straight for that mode to go speed vs speed, but it was still too slow to pin Kizaru down and got sent flying. Luffy has FS too. After getting cucked in Snakeman, Luffy goes G5.
Seems like Boundman and lesser gears are too slow to be effective against Kizaru.