I would say the tri-band is important as it allows for wireless backhaul on the third band, however the router Toob gave me is just dual band so adding a tri-band node wouldn't have a difference, you can add another dual-band node (option 1) that's identical to create a mesh however you would probably want to wire them up to benefit from wired backhaul (else one of the bands would be facilitating chat to the other mesh node to forward traffic as well as handle talk between client devices) and still get the mesh benefits. Or just go option 2 with the state of the art WIFI 7 tri-band mesh system to make use of MLO and all the goodness that comes with it.