VTwinFx.app is need to run the older versions of our plugins before they were Apple Silicon native. If you still intend to use any plugin in Rosetta2 mode then you need to keep this application installed and we recommend you tick the "don't show this again" checkbox. Reminder every time you want to use our plugins that are not yet native you must launch FCP in Rosetta2 mode using the launcher from here:
how to use plugins which are not yet Apple Silicon native
Once you are sure you don't need the Rosetta2 versions you can delete this from /Applications/CoreMelt or by using the "Remove FxPlug3 version" option in CoreMelt Manager.
See here for a list of which plugins are Apple Silicon native.