Am pretty sure Level 4 Seraz are never tradable, no matter how you get them. Not even with Scrolls. They are always marked as event items.
Trying to remember back to the last server they did like this, I think the XP was 700% at least. Maybe 800%
I do know I managed a 80 Zerk, a 89 Ranger and a 83 Knight last time to be my perma buff toons.
If you are making a buff toon only, probably nice to get it to 90 so you can put +2 HH top on it for uber buffs in HH. Level 80 also if you think you can manage a HH80 Top.
All my CC items came along with the transfer no problems last time.
One fun thing to do is to have a leveling race with friends. Each picks and makes a level 1 toon. Someone gives the GO, and you all race to a certain level, say 30. First one to be at a pre-arranged spot at that level is the winner. All be in a party at the beginning to ensure no head start cheating