Cat1 boards are newer yes, and in general are less complex and a bit more reliable, at least in theory between Cat1 and Cat3. They are pretty much a replacement.
Cat1 are for devices which require less data usage (like the alarm panel) and helps minimize the power requirements/etc.
Ah, np! The Image Sensor does indeed use cellular, but static images from the image sensor do not approach the requirements of a video camera. Happy to help!