I recently bought some Deco XE75 units to replace my M9+ nodes. I’ve been approaching the advertised 100 device limit of the M9’s for some time now and wanted wifi6. The XE75 advertises support for 200 devices. 

But I miss some of the features of the M9 when it’s used as the main router. The ability to remotely run a network speed test on my home network, Homecare (which is free) vs Homeshield (which I don’t want to pay for), and a QoS which I’m getting the feeling is better on the M9’s.

I was thinking of make one of my old M9 units the main router instead of the newer XE75. 

1) Would I still get wifi6 (assuming I’m connected to a XE75 node)?
2) Is the device limit driven by the unit designated as the main router node or by the node your connected to?
3) Will the network suffer any performance issues by having an older device being the main unit?