I do worry that if I do get them I might hammer my router since the traffic streams will have to be routed between VLANs.
The key here is to not route traffic across VLANs. Choose one VLAN to host all your network video content (IP cameras and NVR). This way, since all traffic is on the same subnet, all the network traversal can happen on the switch (even layer 2 switches) and not need to ever touch the router.
Also, if you suspect there will be a decent amount of network traffic that needs to cross VLANs, it’s usually best to add an additional network interface that’s connected to the correct subnet. That way traffic can avoid the router.