Questions about TP-Link Deco M4 AC1200 Dualband WLAN Mesh 1-pack

I use a single Deco M4 to connect printers to Mac, iPad etc. (without internet connection). It actually works, but the network is unsecured. According to the manufacturer, WPA2 and WPA3 are available. But there is no security key on the product. Operating an unsecured network is completely unacceptable to me.

I have a Netgear M1 LTE router. Can I still create a mesh directly with the M4's? Since the M1 only has an Ethernet connection, my idea would be to proceed as follows. Deactivate the WLAN on the M1 and set up the M4's as a WIFI mesh so that I have WIFI all over the place, plus two LAN connections at each location (e.g. living room) and finally connect a switch for LAN connection in the office where the M1 is also located. What do you think, will this work?