Maybe what I said wasn't clear somehow:
1. Whether Sanji has the power or not, he isn't using it voluntarily. And this would mean that going forward, if he does have it, that Oda gave him an active power that he will not actively use. Dumb writing.
2. Queen assumes he turns invisible. But we have to take this with a grain of salt because Queen also assumes his fire is synthetic. Did the Germa kids have two unrelated powers without Raid Suits? If they only have one then which would be more likely for Sanji to have? Remember that their hair color corresponded to their powers before they even had them. Sanji has blonde hair instead of black, white, silver, clear, etc. So I would say it's pretty likely that the stealth black gimmick doesn't precede his birth.
3. Sanji is fast, but he doesn't use Soru. That's why yes, you will notice a difference. Soru is a specific technique, not just speed, although it's not so different from when he hit Heat anyway.
[automerge]1636212518[/automerge]
All of the theories based on sfx seem dead wrong, if only because the people naking these assertions don't actually understand the stx. They say shit like Sanji has CoC because he glares during a nosebleed lmao. "Fu" for one example would be smoke or wind, like the wind of Sanji taking off or the smoke of the cigar.