Also should add, while you CAN use the 5Ghz radio (802.11ac) for access AND mesh/backhaul, it's not recommended since it effectively splits the 5Ghz radio from dedicated backhaul to treating the backhaul to the same useage limitations as a client.
So if the intent is to provide dedicated backhaul, disable all VAPs on the 5Ghz radios of those mesh APs and let the radios dedicate themselves to the mesh link. If the intent for mesh is NOT dedicated and you want to serve clients and mesh on the same 5Ghz radio, you can, just know the mesh link will not be as stable or as fast (assuming the antennas for mesh and client access are the same).