It looks like OpenIPC is a replacement firmware. I would assume this means (as long as you trust the OpenIPC authors) that you don't have to firewall them off from the Internet. You ordinarily only have to do that for the sketchy firmware that they come with. Open firmware shouldn't be "phoning home".
You never know when a zero-day is going to popup and whack your cameras as IOT, part of a DDOS or whatnot
But if you've hardened it even a little bit with something as easy as not letting it communicate off your intranet, well that can prevent ugly discoveries later
If you need offsite remote camera access you can always carve out a tunnel
For Wyze and Reolink, check out Home Assistant with the ONVIF integration, Scrypted, or Blue Iris - all provide varying degrees of control over these camera brands without relying on their cloud services.
I worked at a video surveillance company many years ago. We built PTZ controls that worked on the desktop and over the network via a web page... this was in early 2000s.
We also got hammered by a patent troll because apparently, the math behind stitching fisheye lenses into a flat video plane is somehow patented.