How can I set the energy settings for the Radioactivity module?
All those cool features are still there, you just need to set up a "Decay profile". You can do this at /admin/structure/radioactivity.

Once you've got the profile setup (with the "Advanced" method by the sounds of what you're looking for), you can edit the Radioactivity field on the entity, and choose that profile. When the entity is viewed, the tracking will kick in automatically.

To respond to events such as fivestar ratings, you need to use the Rules module as everything's been decoupled for flexbility.