so once the card fills it will automatically start to overwrite the oldest files. you wont need to format it.
more than likely the card issues you have read about are issues with the card itself.
here is a link to some info ( user tested) and it might give you an idea of what to use. make sure you are using an “endurance” card that is made for continuous read/ writes. many standard cards ( think of the regular ones you might buy at Walmart) will error because they are made for things like a point and shoot camera, not a continuous HD read write video set up.
currently the only way to backup the entire card is to pull it and put it in a computer to make copies of it.
I know that Wyze have talked about other ways todo this and I’m sure at some point there will be an easier way, but for now, its what we have.