The microphone issues may be caused by a hardware issue. The iPhone 7 and 7 + were notorious for two common issues, Baseband PMIC (power management integrated circuit) and Audio IC failure. Although they’re not really failures. When the phone flexes from being dropped or over normal use, these integrated circuit chips would pop off the board resulting in either the microphones and speakers not working or getting a “No Service” message with a warning triangle next to the service bar status.
As far as the camera issues go that does sound like it may be caused by iOS. Does that happen with both cameras or just one of them?