For the second option, assume that the 20min window is ALWAYS 20 minutes from start-to-finish, but where it falls during the course of a 24 hour day is different from one day to the next (and has no advance warning before the powers shut off).
Edit: I saw a different flying one recently in this sub, and I thought I would share this one that my friends and I have been debating for the last few years
Edit x2: some clarifiers that the people in the comments have sussed out.
For the purposes of both scenarios, the act of flying doesn't use stamina.
Option 2 isn't "You get Superman's abilities", it's "You gain Superman's flight capability"
Option 1's "Max height you can fly is based on your max jump height" is only relative to your starting point. Yeet yourself off a building and enjoy cruising at that height until you choose to land and reset it.
For option 2, the 24-hour clock resets when at the end of the 20-minute window of powerlessness.
For option 2, you are similarly not warned when the 20-minute window is over. It could start and end, and you wouldn't know.
Edit x3: Good golly, another clarification
For the purposes of not creating a horrifying plasma ball a mile-wide every time we take off, let's say that the universe (and your physical flesh) is able to absorb the brunt of the energy exchange required to take off, SAFELY AND GENTLY land, and a basic protection against air friction while flying.
So, no super armor and unbreakable bones, although if you are actively flying, you'll be protected from the wind drag.