View Previous Excel Spreadsheet Version in SharePoint Online without Restoring

Due to the new AutoSave option in Excel (which I've turned off by default) my colleagues are inadvertently making changes to Excel spreadsheets that they're essentially only trying to review.  My guess (from speaking with them) is that they're just enabling certain table filters or slicers in the data, or  perhaps resorting records as they review certain spreadsheets.  However, I can't really be sure that no data has changed and that has me concerned.

Ultimately, I want to compare their version with the previous version to review what has changed.  While Microsoft Word for Office 365 has great mechanisms for doing this, understandably spreadsheets are a different beast and that sort of web-based comparison doesn't seem to be available yet.  What I'd like to be able to do is take the previous version (download it if I have to) and compare it against the current version.  And in the long-term I've reduced the permissions for the document library folder so more people have just "View" permissions but no "Edit" permissions.

Here is a image of screenshots that shows what I'm running into.

https://www.screencast.com/t/1bT6y33C0t

Any help for a better workflow or suggestions on what we should be doing would be appreciated.  This is pricing documentation and while I want people to quickly review it, I don't want any edits to be made unless they're reviewed by multiple people and approved.