Can I turn bowls on a midi lathe like the Jet 1221VS?

Yes, within limits. The 1221VS has a 12" swing, so bowls up to roughly 11" in diameter are practical. Reviewers on r/turning and the AAW forum note that for anything larger or for production bowl work, a 16"+ swing full-size lathe (such as the Powermatic 3520C) is the more appropriate choice.