I bought the standard size when it was the only size available, great to learn on but i felt quite limited with it. I sold it (to an elderly woodworker with no CNC experience, no less!) And bought the XXL. My advice if you’re tight on room is go the XL, try and make it work.
CNC is intimidating, and I came to it with 3d printing and CAD experience. However with the ebook @Julien has developed, all the documentation that @WillAdams linked to, the carbide3d support team, and (most importantly) the amount of helpful people on these forums, you can definitely succeed at it.