Air DB floats on ground CH. It's an extremely short float, though. I was able to do:
CH DB > FRC > land > 5K/c.S > jP > jK > jS > dj jK > jS > Ensenga.
Does not float raw.
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Unrelated to that, unless the entire cast has gotten a damage buff, Johnny himself has gotten a noticeable buff.
Johnny can't double jump after a super jump, but can air dash. He can also air dash after 2 jumps during a Dust. (not sure if the latter is relevant though)
New coin doesn't knockdown in air, it acts just like a regular hit.
High coin is obviously timed so that is it meaty off of 2D.