sorry Swane, I thought you were talking about refractors! So ignore my ramblings up above
Yes, the F numbers are the same as the photographic F numbers. Just the focal length divided by the aperture. It's really only significant for astrophotography. Visually it mostly comes down to which eyepieces you use.
Your guesses are spot on regarding the mount problems. As a starter scope for purely visual use the mounts might be adequate, but for serious astrophotography you need all the stability you can get. You also need very accurate tracking, which I doubt those mounts would offer.
As far as the optics of those scopes are concerned I really can't offer any opinions.