Talking about the APEX$_ tables: If you are not using any Websheets applications, it's safe to drop them. This won't interfere with any of your regular APEX database applications.
If that changes later on, upon creating your first Websheet application, the wizard will detect all missing tables (even corrupt tables if you happened to alter them). A dialog comes up telling you "The database objects required to create Websheet applications are either invalid or do not exist". Click on "Manage Websheets Database Objects" and easily recover them in another wizard within just a few seconds. And you're done.