Bearing Retaining plate and jointing compound
The retaining plate you are talking about has always been a mystery to me since as stated in the post the outer race has a circlip groove for a circlip to prevent the axial movement of the bearing in the crankcase. Further, the bearing outer race is on many engines proud of the crankcase face so that the plate is not flush with the crankcase face so that the retaining screws tend to buckle the plate when tightened
I have always not fitted this plate and never had a problem.
I have used Loctite 5922 Flange sealant very successfully, available in a tube and you can paint it on the joint faces with a small paint brush.