Can I set my max heart rate and zones?

Yes, on Settings > Your athlete profile. Type your max heart rate and you immediately see the five zones it implies. Below that, a heart-rate zones card lets you set your own boundaries in bpm, checked as you type so a split the rest of Trailwise could not read is never saved. A value you set yourself is never overwritten by a connector, and the card says where your zones came from. If you have not set a max heart rate, the zones card asks for one first, because there is nothing to divide into zones without a ceiling. Your scores still work: the engine falls back to an estimate from your age, and for women that estimate comes from a formula worked out on a female cohort.