Think about it. just like matsuri and arena, the event requires people to register to effectively match based on it's criteria (level first then power, which we all know is flawed). If the top bracket needs more people, it would grab people down below. Leveing also causes this placing and eventually you be moved back if someone else levels with a much higher power than yours, which happens to me a lot. Sometimes, I get bumped down to a bracket that is almost the same as my typical bracket and it is usually due to registration. Brackets should be more stable once we have more people reaching the max level.

Not entirely sure but i think Garv is right, it kinda depends on how many players signed up. I freeze at 93 and I have fought lvl 88 and 99, not in the same sage but different times. Anyway if you are lvl 88 you should expect to find some low 90`s people in your sage sometimes

it depends on how many people register. People are distribuited in various fields depending on the total number of registered players.