Marco has never shown feats to put him above G4 Snakeman speed. Clashing with Kizaru doesn't show that.
I'm still quite doubtful of the idea that Sanji is faster than Marco to be honest. You say Sanji is base on his feats against Queen but Marco was holding off both King and Queen therefore you can't really say well Sanji is faster than Marco either but for devils advocate I'll say okay even if he is that doesn't put him above G4 Snakeman which is so fast that FS Level user like Katakuri struggled to keep up.
I thought you were saying because Marco clashed with Kizaru that means Marco is faster the Snakeman and because Sanji is faster than Marco that makes Sanji faster than Snakeman right? That would imply you're saying current Sanji is as fast or faster than Kizaru.
I don't disagree and you're the one underrated him currently putting him below Sanji.
He came out of nowhere and stopped kizaru's attack, that's a pretty good feat and that puts him above snakeman wci
He is faster than snakeman pre wano
Marco holding back king and queen at the same time doesn't change the fact that he attacked them individually, he never blitzed queen to the point where he seemed invisible for him, even when he was attacking
Sanji's travel speed>Marco's attacking speed
And no, being faster than Marco doesn't mean being as fast kizaru
I'm not underrating him, I still think he can beat any first commander+sanji aside from Beckman high - extreme diff
He's just slower than Sanji, but he has other abilities to make up for it