I have an existing mesh network (TP-Link EAP615) with a hardware controller (TP-Link Omada Hardware Controller ).  Since I have 2.5GB lines, I want to add the EAP660HD but I'm wondering if that can be incorporated into the existing meshnetwork and how mixing different access point with different speeds would effect performance.  

Should the EAP660HD be mixed with TP-Link EAP615 in a mesh network?  What are the performance considerations.

Thanks,

Brian