My current setup consists of 3 Deco M9 Plus. Both satellites are connected to the main unit using a wireless connection. Close to the satellites I consistently get 350Mbps download speeds. However, far from one of the satellites the connection is not fast enough. Moreover, I have an increasing number of devices that support Wifi-6 and would like to have support for this at the main node.

I thought I could resolve this in the following manner: add one XE75 as main unit, and move the M9 Plus to a further location to extend the network's reach. I had the impression that as main unit the XE75 should perform better than the M9 Plus.

However, in practice this didn't work. When I put the XE75 as main unit and put my laptop next to a nearby M9 Plus satellite the following happens:

* when my laptop connects to the main XE75 directly, I still get around 350Mbps at this location (the speed the M9 Plus satellite originally also provided)

* when my laptop connects to the satellite M9 Plus, I never get more than around 175Mbps (around half of what it was before)

It is as if the satellite M9 Plus is not able to fully exploit its dedicated wireless backhaul to the XE75. Indeed, when the M9 Plus is the main node, according to the Deco App the satellites are connected using 2.4Ghz/5Ghz_1/5Ghz_2, but when the XE75 is the main node, this is only 2.4Ghz/5GHz. 

I have the impression that 5Ghz_1/5Ghz_2 is necessary to get a full speed wireless backhaul, which the XE75 does not seem to provide. 

Is this correct? Is there any Deco unit with Wifi-6 support that could be used as main unit and that would allow M9 Plus satellites to obtain their maximum speed?