My understanding is that dnsmasq on the router is required for VPN policies to work with domain names. You can try configuring the GL-AXT1800 as the main router and the ASUS router as a wifi access point:

internet<-axt1800 (for dns+dhcp+vpn) <-ASUS router (wifi access point)<-devices

I do not work for and I do not have formal association with GL.iNet.