I have a 3-bed house, half of which is basement, so Wi-Fi is an issue. I'm using Google Home smart devices (2.4Ghz). I have a mesh comprising 3 x Deco S7s and 3 x E4R's. 

I have a Virgin Hub 3 upstairs with the main S7 connected directly which serves the ground floor via 2 more Decos. The main E4R downstairs is connected by Ethernet to the Virgin hub, with my alarm and door entry  connected via an Ethernet switch.  This satellite Deco serves the other two E4Rs. Currently, the Hub 3 is not in modem mode, thus I have two Wi-Fi networks but only use the Deco Wi-Fi.

It has been suggested that I should put the Hub 3 in modem mode. Apparently, this means that only one port will work, which will  connect to the main Deco. An Ethernet switch connected to that Deco would provide the other ports.  Is this the way forward?

I should mention that I have a spare AC1200 Wi-Fi router and a Wi-Fi repeater supplied by Virgin which are not used. Could these be used to further enhance the set up?

Suggestions gratefully received. Please bear in mind that I am less tech savvy than you might suppose :-) Thanks