I really like the Plex interface and how it organises all of my media based on the metadata but my laptop overheats and the fan turns on when watching within Plex.
Is it possible to use this interface then open directly in the default video player (e.g. VLC) without having to watch within Plex?
No – you cannot do that directly from within Plex.
You could enable the Plex DLNA server and access that through VLC.
As for the overheating – that sounds like the server is transcoding a lot in order to play things. Have you considered getting to the core of that?
What player are you using on that Mac – Plex Web through your browser, Plex for Mac or Plex Media Player?
The Plex desktop client and Plex Media Player should actually be able to play most files without much transcoding.
Could you share some more details on those files?
e.g. the content of ... > Get Info – or even better click on View XML on that dialog and copy the content between <Media> and </Media> in the file being displayed in your browser.