There are 3 kinds of arenas in Eden Eternal: 3 vs. 3, 10 vs. 10 and Monster Battle Arena.
3 vs. 3 has the following brackets:
- Level 30-39
- Level 40-49
- Level 50-59
- Level 60-69
- Level 70+
10 vs. 10 has the following brackets:
So as you see, 10 vs. 10 is only for higher Level players.
Finally, Monster Battle Arena does not have any level restrictions at all, so a lvl 30 can be paired with a lvl 75 here. There are, however, special weapons to kind of compensate for that (which in practice isn't really working).
Apart of the arenas we also have Territory War and Elysium Island as PvP places. Those are both special and cannot be compared to arenas though. For them, the same rule as for MBA applies: No level brackets.
I hope this helps you a bit.