An additional observation on MAU to User ratios.
Of 150 largest instances (min 8k users, extent of my "analysis"), the MAU/Total User ratio had no relationship with the total user count. Said ratio varies from 0-40% with outliers 48, 53, 75%.
Though, all high MAU ratio instances are small.
That is: all >30% MAU ratio instances have ~30k or fewer users. So small instance community is probably working well, but not reliably so?