Hi - (a) We may watch any videos we like no matter which challenge we pick. (b) Each challenge has its own leaderboard that ranks the wellbeing minutes of its participants. We may only be in one challenge at a time so that the leaderboards will correctly tally participants' minutes. (c) Pick a challenge based on whose participants' feeds and whose leader's guidance interest you most. Then do whatever activities you like! (I happen to be doing BOTH Pace and Go's AND Sarah Kusch's 30-day mini-video series simultaneously. No need to stick to only one.) Enjoy! :)

I haven't found any way around being part of only one challenge - even with multiple Challenges open the page says I am not eligible to join another Challenge once I have joined one.
Peace of Mind: https://grokker.com/challenge/baby-2023-peace-of-mind/6391159d4954600fb73ad349
Daily Meditation: https://grokker.com/challenge/baby-2023-daily-meditation/639115934954600fb73ad346
Cooking Possible: https://grokker.com/challenge/baby-2023-cooking-possible/6391158a4954600fb73ad343
Better, Faster, Stronger: https://grokker.com/challenge/baby-2023-better-faster-stronger/639115a84954600fb73ad34c

I assume the limit of Challenges is 1, but let me know if you find a way around this. Thanks!