How does Rio Music Manager compare to emplode. Does it work as good for changing track info.

The tagging UI is the same as in emplode -- I lifted the code directly. Moreover, it allows you to use the same UI for editing the tags on files on your PC (in your Media Library).

Does the karma have it's own database like the empeg or does it just use the tags.

It has its own database. It's not the same as the empeg's database. It supports UTF8 and is better optimised for memory usage.