Hi @ChickenSnitz . Is this the Asus RT AX56U? In the manual, it looks like this model has no Access Point mode.
Change Asus LAN ip address to 192.168.1.2, disable DHCP and NAT, and connect LAN port to LAN port. You can set the Asus wifi to same or different settings as VR1600, or disable VR1600 wifi and just use the Asus.
Do you use the VOIP phone function on VR1600? If not, you can put the VR1600 into bridge mode. The Asus works as normal wireless router. Connect Asus WAN port to VR1600 LAN port.