I was wondering if there is way to compare the previous schedule with the current schedule at a total level roll-up? If so, does it drill down to the details and reflect what changes were done from the previous to the current by task?
From your description, it seems you have not (yet) found the “Compare Projects” tool (on the Report tab/ribbon in MSP 2016). That tool is intended to compare two versions of the same project, using the task/resource Unique IDs as comparison keys. It examines values in the specified tables from the two projects, then it combines those values and their differences in a new “Comparison Report” project. Differences are identified cell-by-cell, including all detailed and summary tasks. Any roll-ups occur before the comparisons, not after.
1. The comparison report requires a fair number of custom fields, and this limits the number and types of fields to be included in the compared tables.
2. If the project files have been managed in a way that fails to preserve the Unique IDs from version to version, then all bets are off.
Good luck, tom