Yes, you can: Wireguard VPN setup Every qube that is connected to this (service) vpn qube will be routing its traffic to your vpn provider.
This is not a Qubes related question. But if you configure your VPN on a router your benefit is that all devices connected to this router will be using your VPN automatically, no need to setup VPN configs / apps on your devices. An other advantage is that you can connect unlimited devices to your router (VPN provider limits your number of devices per account). Obviously, your disadvantage is when you are using your notebook or smartphone outside your home network (your VPN router) your traffic will not be forwarded to your VPN provider.