The Most Important Recovery Metric?

The most important metric, if you could pick only one, I would say CTL. How far can your true CTL be if FTP is set incorrectly and what's the worst you've ever seen? Can we quantify TSS when training off the bike or does it matter? Is there a better way to track sleep quality than PMC? Are there any metrics to use to determine when to switch from base threshold,. VO2 to race, etc.?