Hi @Eraserhead ,
Could you please share a bit more about the issue?
Do you mean the Option Set field and Lookup field acted as String type in your Edit form rather than "Complex" type?
Based on the issue that you mentioned, I have made a test on my side, and don't have the issue that you mentioned. Actually, it is not necessary to add D365 connection in your app, instead, you should add corresponding CDS Entity as data source into your app.
Note: The D365 Entity is based on CDS Entity, which is in same PowerApps Environment (D365 instance).
Please consider take a try to generate a new app based on the corresponding CDS Entity, then check if the issue is solved. In additon, please make sure you have refreshed the data source manually in your app after you add a couple of new fields to your Entity.
Best regards,