WoW1 recruits WoW2
WoW2 recruits WoW3

WoW2 and WoW3 are linked for RAF even when you got a highlevel char for boosting logged in on WoW1

You use your highlevel on WoW1 to kick the toons on WoW2 and WoW3 through the instances.
(you can do this until level 80).

2 chars on level 80 = 80 levels can be granted to WoW1 via WoW2 (in case you are missing a class on WoW1)
2 chars on level 80 = 80 levels can be granted to WoW2 via WoW3 (for your pair of classes).

when you got all chars you need fir your pairs on WoW2, just disable WoW3
and play WoW1 + WoW2 as dual-box.