Free: None I've had too many bad experiences of people just not giving a shit there

Casual: up to 5 usually maybe 4 if they are more high casual.

Advanced: I've never really felt like writing a novel with other people as I do it by myself, rping casual is enough to get me going and motivated to write.

1X1s: Normally just one, maybe two as they are far easier to keep up and track with as it's just two people. Normally casual to high casual for me regarding them as well.