If you are to set up VPN on the router then internet connection via the router will be by VPN. Security cameras will have their own software or mobile App to do it and do not need wireguard. I also have camera at home.
It is okay, I think average users tend to know more about
VPN clients (through the use of Corporate VPN or commercial VPNs like NordVPN and Surfsharks). But they do not understand the use cases of
VPN servers.
Security cameras nowadays will have apps for remote access. That is just one use case. There are other use cases where VPN servers from the home router or home network may be useful. I guess you do not have or do not know those use cases. No problems with that since it might be a more advanced topics for you.
One simple reference from Asus.
https://www.asus.com/sg/support/faq/1050842/
ASUS router can function as VPN servers, allowing remote devices to securely connect to the home network from anywhere. This enables users to access their home network resources securely when away from home.
ASUS router can act as VPN clients, connecting the entire home network to a VPN service. This provides VPN protection for all connected devices without needing to configure VPN individually on each device.