CEC vs FSW vs FST — I qualify for more than one, does it matter which program I get invited under?

You don't pick — all three programs (CEC, FSW, FST) feed the same pool and IRCC assesses you against whichever you're eligible for at the ITA/application stage, using your profile answers. Practically, what matters more is making sure your profile accurately reflects experience/language/education for EVERY program you might qualify under, so you're not accidentally screened out of one. See /guides/pr/cec, /guides/pr/fsw, /guides/pr/fst for the eligibility differences.