Hi gunen,
Yes, you will need to change the accuracy settings to match the accuracy of your PPK system. I guess a value between 0.02m (= 2cm) and 0.15m (= 15cm) for camera accuracy is realistic using PPK (will depend on the 'quality' of your system though). Leave the camera accuracy (deg) at the default value.
Make sure that the cameras are checked in the REFERENCE PANE to guarantee that they are used as a reference.
After image alignment you should always 'clean' your sparse point cloud using EDIT > GRADUAL SELECTION. Remove all points with high reprojection error (choose a value below 1, I suggest to use 0.5-0.8 ) and high reconstruction uncertainty (try to find the 'natural threshold' by moving the slider). After you have removed 'rogue' tie points from the sparse point cloud, run the optimize camera alignment step.
To verify your model's accuracy, you could/should include a few scale bars. Simply use a tape measure to get the distance between obvious points/objects before you fly. You could put down a few GCP markers and simple measure the distance between them, for example. In Photoscan, add them as check scale bars (not control scale bars), which means they are NOT used to optimise your tie points (sparse point cloud) and camera locations and orientations. Hope that makes sense.
All the best.
Regards,
SAV