looks like someone threw a twin hull catamaran, a flying saucer and a klingon warbird into i blender and ended up with a not half bad looking federation ship that they decided would play no major parts in any movie because it looked too cool.
No major parts in any movie? Tell me you didn't type that. That thing trashed the Enterprise, was Ricardo Montalban's personal soundstage, and was Ground Zero for the only full-scale Genesis deployment ever.
It just looks 'right' to me, being a slightly more recent addition to the Federation's Starfleet, and having some toughness that's characteristic of the Constitution-class; a good sibling you could say.
As far as its classification, i.e. frigate, destroyer, et al, I was given the impression that it was a 'research cruiser', hence the reason why it was looking for a suitable planet for the Genesis Project. The double-rear hangers (partially visible in the profile view) would be a suitable launch of various shuttles to planets in a star system.