Note: many stores do not need addons. If you need an addon later on you can purchase it at any time.
The secondary cache makes your Web site fast even after a user logs into their account or adds a product to their cart or completes another action that makes using the primary cache impossible. For very busy Web sites or extremely slow Web sites, it makes sense to use the secondary cache. If you have a limited budget, then you can wait to upgrade to this at a later date. Otherwise, this addon is recommended to ensure your Web site is as fast as possible at all times.
Tagging / Auto-flushing is designed for stores that make frequent changes and cannot tolerate showing outdated information. With auto-tagging / auto-flushing your cached pages will be precision-flushed after editing products, categories, and cms pages. This precision flush will not affect other cached pages. Without tagging you would be required to flush the entire cache in order to guarantee fresh content is shown or else run the crawler to help freshen the most important pages.