What are some of the legacy files from upgrading from a 7135/600 to a 650 that may have been transfered to the new 650 that can be deleted?

I thought I read something one time that contacts were in a new file/database in OS5 versus the setup used in OS4. Can the OS4 based files be deleted or are they still used?

What other items can be removed that may have made it over during the transition?