Question Apple Airport compatible with Synology MR2200ac? As far as I know, the mesh systems must be from the same manufacturer. This means that the Apple Airport system cannot be integrated.

Buy RT2600ac with MR2200ac? Yes, according to Synology's documentation this makes sense. I myself use the RT2600ac with 3 MR2200ac over two floors. It also works reliably with many devices in the WLAN (20).

I don't know the Apple Airport. However, I don't believe that you can connect the Apple Airport and MR2200ac together to form a mesh network. With two MR2200acs, one takes over the function of a second router next to the Airport and a second MC2200ac can then make a network with the first. So there would be two WLAN networks after all. I myself have the combination of RT2600ac and three MR2200ac. Together they form a network. This works perfectly. To get an even better signal, you can also connect the MR2200ac to a LAN cable on the WAN port after the MESH network has been formed (this only works via WLAN). Then each MR2200ac automatically has full power and it is the same WLAN network everywhere in the house. LAN cables are recommended if the WLAN of the nearest router does not come through well. This is possible with Devolo plugs, for example. As I said, I am very satisfied with it, also and especially with the RT2600ac.

I can agree with Heimzgi75's statement. The RT2600ac set with three MR2200ac also works perfectly for me. The connection of the MR2200ac via rooms and/or floors only works reliably via Ethernet or powerLANs. I don't know what the developers were thinking in connection with rooms and floors and the additional, internal "data channel" on 5GHz. Mesh
will only work within the system and not with third-party components. The familiar Synology operating system, the configuration options and the regular security updates persuaded me to buy it.