Which takes precedence, image quality configured through Portal (on the Form builder) or image quality settings on the device ('account' tab image quality)?
The server's configurations on each image-based question should almost always take precedence and override what the users device is configured to. The only time this does not happen is if you have the following settings turned on for that image based questions:
If this the above setting is turned on than anything on the users device will overpower what the server has.
Any other option (i.e Small file, Average quality or High quality) will mean that these settings will override what is configured on the device.
If you have any questions on this please contact Support at firstname.lastname@example.org