Long story short, a friend of mine, who have much more advanced audio gear than me, got this. I haven't been able to spend much time with it, but I'll try answering with what I know.
There is a shit-ton of presets. So much in fact, that you can really waste hours just trying them, without even turning a knob or changing a parameter manually.
Will they make you lazy? Perhaps. Let's say that if you're just starting out, it might be tempting to rely heavily on preset.
Alas, skipping on learning how things work, and pretending you've spent 3 hrs working on your mix when, in fact, you just pushed a button won't help you in the long run.
One shouldn't make that mistake, for you'll be passing up on one very powerful piece of software imo.
You can most definitely take these presets as a starting point to understand how they affect each area of your mix.
You can bypass effects in real-time, target a specific channel only, hear your mix in mono with or without said effect, isolate a frequency range and hear (see) the results real-time too, take snapshots of your mix to gauge the impact of changes made on equalizer thus maximizing your mastering efficiency.
And there is much much more depth to this, but I digress, and your questions were about presets, so here goes!
From my short experience with O4, the most useful presets were the solo instruments / instruments group related ones (bass, cello, guitar, brass section, piano...).
The global presets (multi-bands / gate, tube, compressor / cd master...) have a tendency to go overboard, and toss harmonic exciter and loudness maximizer all over the place, or simply aren't gonna be adapted for every style of music.
So yes, there are genre specific presets, and some will work like a charm (rock / electro / hip hop / reggae). But some won't be as effective...
Finally, the Utility presets have some usefuf ones for vocals, for creating specific ambiences, or for sound modeling.
BUT, and I insist on this, once you're done playing with presets, really try to delve into each specific tool.
There's an amazing amount of control in this thing, and unfortunately, I've barely had time to scratch the surface.
So yes, it's very possible to do one-clik mastering. But then again, I'm not sure how many audiophile it would succeed to fool...
Finally, I can't answer for question #3 since I've only tried Ozone 4. That would have to be your call.
Anyway, hope this helped.