Deco Mesh Help

I will be receiving a WD My Cloud Home Duo this coming Friday. I have an Actiontec router from my ISP with an available ethernet port. The Actiontec feeds my Deco Mesh system and that is the de facto home network (the Actiontec router radio is disabled. If I connect the Cloud Home Duo to the actiontec, will I see it on the home network? Should I just make the Duo available through the ethernet connection on the Deco Mesh? I’m trying to avoid headaches when I get to setting it up. Any advice will be greatly appreciated,

It is recommended to connect the WD My Cloud Home to a network router via Ethernet cable:

https://support-en.wd.com/app/answers/detail/a_id/2664

This much I knew. I guess that I wasn’t clear enough. Nonetheless, I have connected the My Home Duo to the Deco via an Ethernet cable. I’ve switched to Raid 0 and went through a few hoops to reconnect. I directed my deco to assign a static IP versus a dynamic one (in case that would be a problem). I then connected a WD external HHD via USB C to the My Home and started file transfer. My problem now is twofold. First, I can’t seem to find any way to have Plex remove the old server and I don’t see my files on the My Home. I realize that I’ve placed a lot of information here, but perhaps you can help.