How impressive is an extensive theater, music, performing arts resume when it comes to auditioning for performance arts?
It's good to have breadth of achievement but don't forget your commitment to these individual pieces also matters! Quality over quantity, as cliché as it sounds, is always the best route for college admissions. As long as you are doing activities you enjoy, the amount is not as relevant.
When auditioning, it mostly depends on what you are specifically auditioning for. I think that if you show great focus or dedication towards theater and you're auditioning for something in theater, it would look a bit more impressive than having equal commitments to marching band, orchestra, chorus, and theater. It is great to have a variety of interests, but I think that being a bit more specialized or dedicated towards one would be favorable. My sibling was in performing arts as well and he was in a specific program at a performing arts high school. In order to show that he was dedicated and talented, he auditioned for things such as All State every year and his consistency in winning or getting into bands at a high level was impressive. It depends on whether you have the mindset that colleges want a well-rounded person or someone with a big spike. I think you should (if you have the time still) hone in on one in particular that you enjoy the most or feel the most confident in and strengthen your resume while being specific to that. It all depends on where you're apply to or what you're auditioning for, but specifics (especially in your dedication or passion) are important. Hope this helps a bit! Good luck :)
If you have lots of achievements, particularly in regional/semiprofessional or higher theater productions, that can really help in standing out at performing arts school auditions!