Setting up a VPN server on your home's router is only for securing connectivity IN to your local network from the Internet from specific devices (aka your phone). Any traffic emanating from inside the home OUT to the Internet will continue to pass through the router as it does currently (without a VPN server running). Establishing a VPN connection to view your cameras from the Internet will consume part of the home's Internet bandwidth. This will occur regardless of how you connect remotely to stream live video that is not cached. Keep in mind watching security cam feeds is different from watching a video from Netflix, amazon, hulu, etc (these services cache/buffer the content)
