Hello,
The increment value depends on the record type although most are incremented by one. There is a record type that is incremented by 20 as it is cached.
When are they incremented depends on the record type. For example, a cell_package_sk is incremented placed in the diagram and when execution happens.
Yes, the maximum + N (1, 10, 100, 1000, etc) is best to avoid constraint conflicts in the CDM.