@Rodorom 

The best way would be to use what you already have. TP-Link AC3150 router is not WiFi mesh compatible with Deco mesh, but it can be used together with Deco to achieve what you want.

Here is how:

1. Make TP-Link AC3150 your Main Router;

2. Turn off TP-Link AC3150 router WiFi, you will only use it as wired router;

3. Connect Main Deco to TP-Link AC3150;

4. Configure Deco mesh to run in Access Point mode: Switching a Deco to Access Point (AP) Mode

After you've done that, you can use TP-Link AC3150 USB ports for printer and external drive, and those will be accessible to anyone connected to your home network.

You can also use TP-Link AC3150 Ethernet ports. You can hardwire to them anything you want, including Satellite Deco.

As for expanding Deco X50 network coverage, with above setup it would make sense to buy more X50s for that. 

 
@Alexandre. 

Thanks Alexandre for your quick reply. I like the idea of using the Archer C3150, but not sure this will work.

The incoming fiber is completely on the other side of the house compared to the office of where I would need the Archers USB. My main Deco is positioned in the center of the house with a wire to the incoming fiber. Is there any way to connect the Archer to the AP in the office instead and use it for network printing? If not, is there a way to do this with other routers?

  @Rodorom 

You can try configuring TP-Link AC3150 in Access Point mode and connect it to Office Deco by Ethernet cable. See How to setup an AC-class Wi-Fi Router as an Access Point (New Blue UI)

In this document, your "Root router" will be "AP Office Deco."

I can't tell what features AC3150 will keep in Access Point mode, for example if it will allow using USB ports, but it is worth trying.

  @Alexandre. 

I followed the link for connecting the AC3150 as an AP. And I managed to make that part work. However I can't seem to login to the Archer any longer. The buttons in the USB printer controller tool are all grayed out. On the archer the USB light is lighting up when connecting the printer. So in order to test if no other settings were wrong I tried to make it work by reconnecting the archer by wire to my computer.  Then try to get in tplinkwifi.net or the IP I gave it when following the instructions you sent. Neither gives any reply, so it seems like I'm locked out of the Archer now. Any suggestions?

  @Rodorom 

I can't explain why you can't login to router running in AP mode. This FAQ document make it look easy: Archer - Configure Access Point Mode

You can also check this document How do I log into the web-based Utility (Management Page) of TP-Link wireless router? and if nothing helps, use factory reset button to recover Archer router.

If you can't manage to get access to AC3150 running in AP mode, other options are:

1) Connect printer to desktop and network share it; 

or

2) use USB print server such as Cheecent CR202 to share USB printer on network - but I glanced at its documentation and this may require some technical skills to set it up.

There is Deco model with USB port, of latest BE series (such as BE65), but it is not good fit for your Deco mesh and it is expensive - so makes little financial sense. If you are ready to spend that much, look for a new printer with Ethernet port instead.

  @Alexandre. 

Thanks for your quick replies. I gave up on the Archer, there's no way to access it other than factory reset and it still no guarantees that the printer will work the way I intend to. I'll make an attempt for network sharing instead and see if that will be easier to set up. 

Thanks again for your help.