There is two caches that Lr is using.
One is the previews cache, mostly called previews folder which is located next to the catalog file as a folder with the extension < .lrdat>.
Then there is the Camera Raw cache. You can see its location and size - and change the size - in Preferences / File Handling tab. It does not contain any previews.
The previews (in the previews folder) are used in the Library Module where Lr displays the "canned" previews - basically JPGs that have been created after import.
But in the Develop Module Lr works with the actual Raw file. It is only in this process that the Camera Raw cache is used. The previews are not used in the Develop Module.