Re: I am feeling a lot of confusion after upgrading to version 3.0..help.
Let us know what your end goal is, and we can help point you to the right approach.
We have been planning to get rid of the cache tool for a long time. The osgEarth cache is meant to be transient (like a browser cache) and not meant as a persistent data store. Despite this, people used it to create offline datasets or pre-tiled data, but this was not its intent and there are better tools for those jobs.
This section talks about ways to prepare your GDAL-compatible datasets so they load quickly. It also explains how to use osgearth_conv to build portable pre-tiled datasets: