It does consist a lot of challenges but that's not everything - basically there's the two teams (Red Rose and White Rose in that case) that compete against each other via challenges... Those can be everything, from writing to graphics to stamping (currently we have a "Which of Henry's wives are you?" stamping challenge running and it's amazing) to puzzles and games, and everything... You don't have to do all of them but maybe one or two per month-ish (or even per phase?), so basically just pick the ones that look fun to you :D Those challenges earn you points then, and the team with the most points wins the "cup"! (Which is really just glory and fun, haha.)

There haven't really been discussions in this particular comm, but I'm sure that you can always start them, especially in your team comm! And you don't have to sign up for certain fandoms at all - just use whatever you love that is eligible for the comm theme (unless there are special instructions), and you're all good!