Are the files removable from the Apple app to VLC app?
Yes, they are. Select any file of the type you want to change. Hit Command-I, or Get Info from the file menu. You see a thing that shows the default app handler for the file in the Info window. The current handler is the text of a typical dropdown that allows you to change the handler to a different app.
You can also make the change of handler universal (for all files of that type, in other words). I did just that with mp3s. When I have loops or small mp3 files I just want to open them in QuickTime, rather than have iTunes launching. So I changed the handler to QT. Easy.
When I am in the iTunes environment, itself, the mp3s in iTunes open and play in iTunes, But if I want to go into my directories or Desktop (whatever) and listen to one thing (even a track that also would appear in the iTunes library) it'll open with QT. Fast, simple, etc.