+1 for Tailscale. Tailscale performs better in many people's experience, and has a substantially better free service plan compared to ZeroTier, especially lately as ZeroTier has been reducing what is available to new free sign-ups in recent times.
If you won't be using the NVR, and you trust the Blue Iris machine to work, then you don't even need a new router because tailscale can run fine on the Blue Iris machine.