I don't see the relation with distribution ports and H-REAP.
The best, to my opinion is :
-If you have 2 Gigs, set 2 ports in LAG. If you want 4 Gigs, set 4 ports in LAG, ....
Note that if your WLANs are hreap local switching, it represents very little traffic to your WLC so you could survive with only one port connected. But then you could have redundancy by plugging 2.