Hub difference
The diffference in front hubs is that the Caper has a kidney bean shaped locating raised area that the wheel half aligns with. Also, the Caper hub flange is thicker (triangle shaped piece. They appear to be the same width.
Also shown is the sprocket side. Notice the Fox one is wider. A person could use the Fox wheels on a Caper for a real close look, but I guess since there aren't Many Capers around it's not a problem..