We have not used the Bizagi process engine yet. We will be testing it soon. I did test much of it as Joget seemed a much a better and easier option. I may consider really looking into the Suite only if there is BRE (Business Rules Engine) in there.

There were only a few.

The deployment works well. The advanced deployment wizard lets you to create a "bex" file which includes all the changes. Over the production environment you should apply this file, you can check for the differences and confirm. It is really important to create version each time you deploy changes to avoid unexpected behaviors over the existing cases.

Yes. From time to time, reports, permissions, profiles that were created in development were not updated in deploy.

No.