Well, that was a rollercoaster lol

Chrollo and Feitan might not be far behind Killua. As in they are not necessarily out of his league

If we are talking Godspeed here (and if I understand what you mean by "out of his league"), I have my doubts. Chrollo seemed pretty evenly matched with Silva and Zeno in terms of speed, so they'd be on the same tier, and while I believe him to be slightly faster than Hisoka, the difference does not seem to be that significant. If Whirlwind Killua is as fast as he looks, I think all these people are decently below him, considering that Youpi could not even see him but he could follow and counter Knuckle when the latter lunged at him. For similar reasons, and also Knuckle's confrontation with Cheetu, I doubt that Feitan is close enough to Whirlwind Killua and Cheetu to be able to keep up with them.