Man, i respect how Oda didn't clown the non-Luffy super rookies.
They're no pushovers.
I suppose the message here is that we shouldn't put ceilings on characters based on their goofy designs and being presented in more of a comedic light.
Apoo was extremely impressive even in Sabaody, doing damage to Kizaru's logia body twice, even if didn't do damage to real body is still more impressive than any thing any other supernova did in Sabaody.
And panels like these put Apoo on similar range as someone like Kidd
Don't think it is a stretch to say Apoo is YC3/YC2
I'd say all supernovas are in commander range anyways
Luffy YC1+
Zoro YC1
Kidd YC2/YC1
Apoo YC3/YC2
Hawkins Killer and Urouge between YC3 and YC4
Capone and Bonney YC4