IM Taper - key components?

I’m trying to put together my taper plan for IMCDA. I’m looking at a 20-day taper, the same length I used for my first IM. For that race, I just kind of went on how I felt and kept the workouts within the guidelines of lower volume and higher intensity. I made it to race day well rested, but definitely not at my peak.

I’m looking for advice/input on how you all set-up your tapers so that you hit the race rested AND at your peak.

Thanks,