I set up my new AX1800 yesterday with Smart Connect enabled which allows the 2.4 and 5GHz bands to have identical details and lets the router determine which band each device connects to. I'm not sure how it is determining which band to use for each device but there doesn't seem to be anything "Smart" about it. The first two devices I connected are desktop PCs in the same room as the router. They were both assigned to the 2.4GHz band, limiting download speeds to under 100Mbps. These PCs are responsible for the vast majority of my network usage. I connected my laptop and phone to the router and both were assigned to the 5GHz band. When I disable the 2.4GHz band both PCs see download speeds of 500+Mbps, but as soon as I re-enable the band they switch back to it with slower download speeds. I thought maybe the router would learn that these PCs are high-usage devices and reassign bands accordingly but after a full 24 hours of usage, nothing changed.

My ISP's router did a better job of assigning bands AND had the option to manually assign bands per device. What's up with that?