I don't know much about routers, so I may be wrong, but I don't think there is any reason why the router would prefer non-VPN traffic to VPN traffic, as I have no trouble maxing my dl speed no matter where a server is, as long as their upload speeds are sufficiently higher than my bandwidth; and anyway my router doesn't even have QoS to discriminate my internet traffic. Also I the speeds on different devices, but I still get a disappointing 1-2 MB/s depending on the server.