Of course he''s going to pitch in 21.
Kopech will start in triple A and will probably be shut down in Late Aug/September. You cannot count on him being in a playoff rotation even if he's good enough.
That's why I consider him in the 2022 "wave". He'll go the full season and be counted on from start to finish.
As for Vaughn, I'd rather have MCCann back and rotate him Jose, and Grandall between 1st, C, and DH.
Of course if McCann is fine with just catching, then by all means, bring up Vaughn to rotate with Jose.