I’m in my late 20s and want to start tracking a few key physiological metrics — mainly around sleep, recovery, and daily performance — but I’m interested in focusing only on data that has strong evidence for long-term health and longevity impact.

For those of you with experience:

• Which metrics have actually been meaningful for improving health (e.g., HRV, RHR, VO2 max, sleep consistency, glucose variability, etc.)?
• Which ones turned out to be noise?
• And which devices offer accurate tracking without locking you into subscription models?

I’m looking for signal > data overload and ideally low-cost, non-subscription solutions.

Curious what has truly moved the needle for you.