@51k-bos 

If you want a mesh system, I would select the Deco as it would be the easy setup and maintain and easy to expand later if needed. 
 

The least expensive if it is just one area that needs additional coverage, consider an extender that has Onemesh. 
 

Two routers work but tend to be more complicated to set up and maintain.

In the past I have used a router and no mesh extender with good results. My new router covers the area okay so I dropped the extender. 

  @ArcherC8 

TBH, I haven't read much about it, but can I use the deco with the AX3200? We have good coverage with it inside the house and the decos look so small, no antenna, I feel like I would need more devices for it be comparable to what we get with the AX3200

  @51k-bos 

As noted above, I do not use a Mesh system or router with Mesh. I did research it fully before my upgrade from AC to AX. I just did not need it to get the coverage I need.

I should note that a router and extender will have slower WIFI speed than a Mesh system as an extender is half duplex.

Based on what I see in this fourm, other fourms, YouTube, and other readings, a designed Mesh system is a better way to go than a router/AP mode and also better than two or more routers using a mesh system such as OneMesh. Google OneMesh vs Deco and for the names for other brands for more info.

As far a setup goes, a Mesh system is more stright forward. Not a big concern for me as I know my way around networks, but for many it would be a concern.

If I needed multiple nodes with the best speed, I would go with a Mesh system and not use routers. My previous use of an extender was before there was Mesh systems.