@chrisTP Archer VR600 is a gigabit modem router and it should be capable of 1 gbps on all of its WAN/LAN ports (even in wireless router mode). Why don't you try to upgrade its FW to the latest...

@_Jarek If the root router IP Range (DHCP server) is 192.168.1.2~192.168.1.100, I would set C80 to be 192.168.1.254 (outside this IP range). Since 5Ghz band coverage is less than the 2.4GHz band,...

@Dashrathp With therRouter powered on, press and hold the WPS/RESET button (more than 10 seconds) until the SYS LED becomes quick-flash from slow-flash. Then release the button and wait the Router to...

@mrtim Almost any TP-Link router could work in AP mode if you don't want to buy a dedicated AP. If you need a Wi-Fi 6 capable AP then for example Archer AX53 in AP mode would do the job. You just...

@charliekthrn Here are some additional troubleshooting steps which you may try as well. On the bottom sticker should be noted which HW version and FW region is the device - details.

@sarpi VX220-G2v doesn't seem to be in the tether compatibility list for DSL modem routers - details.