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VST PlugIns and
AU PlugIns

I was curious if V2 of Crunchessor completely overwrites the old installed version or whether both versions are still available after installation.

If the old version is overwritten, what happens to previous settings when loading projects using V1?

No, new version won't "overwrite" older version simply because DLL has a different name.  You won't lose any settings, and you will be able to use previous version after upgrade.