BT Mesh, is that the round disk-like devices?
If so then, no, you can't put the hub into modem mode as the disks don't have any routing/NAT capability, but if you leave the hub in the normal 'router' mode, then certainly you can use the BT disks. Ideally you should disable the hub's WiFi to avoid congestion, but it has a nasty habit of simply re-enabling itself; so don't sweat it!
