Is it possible to change the WiFi settings in the app or do I have to delete the camera and start over from scratch?
Welcome! 
No. Sort of.
As far as I know, you have to do the QR code scanning thing to change the WiFi SSID/pwd.
But you do not gave to delete the cam first. Also it will remember most of your settings and you can still access the 12 sec clips associated with that cam, and anything on the SD card.
So just a small hassle when updating your WiFi passwords while keeping the cam on the same account…