According to the HomeKit guideline, the manufacturer's App can’t affect the settings of HomeKit. 

If you just turn on/off the night version, it will take effect on Home App. But after restarting the camera, the camera will show the status as that set in Home App whatever you set in eufy App. So, if you want to switch the night vision completely, you should turn on/off the night vision both in eufy App and the Home App.