No help for you on the performing arts stuff.
As a n=1 sports medicine physician - IMO having one or two deep experiences working with a team, particularly in training room settings and with ATCs, is tremendously helpful in preparation for fellowship and your career. If you ultimately want to work as a team physician in a university or professional setting you need the insights into the athlete/sport culture, working closely with ATCs, and balancing the risk/reward of playing with/returning from injuries that may be treated differently in a lay person. You probably/may not be able to get this completely in residency, but shoot for as much as you can experience.
To me mass participation events (i.e. marathons, triathlons) are usually pretty bad learning experiences for sports medicine unless you are deep into the logistics of setting up the medical coverage (tents, on course personnel, emergency planning, etc.) or are/interested in being EM doc. You might see some exertional collapse or heat injury, but not any sort of breadth of sports injuries. If it is a huge track or wrestling meet (i.e. Penn Relays, Mt. SAC Relays, high school state track/wrestling champs) then those are worthwhile mass participation opportunities to do "real" sports medicine as the breadth of athlete and potential injuries/illnesses are much greater while still having the mass participation event component.