1-Yes, it comes with a lot and most of them are pretty good.
2-I haven't done any serious experimenting, but the physics and AI are pretty good. You can modify physics weight, friction, buoyancy, that sort of thing for individual entities.
3-Yes, for individual entities.
4-Is it actually good? Yes, most definitely. Way better than X9 in terms of power. Customer support? I haven't had to use cs yet so I don't know...but so far x10 support in general hasn't been too great IMO. Since it came out almost a year ago, there have only been like 2 updates. Though it says you can on the main site, there isn't yet support for custom soft particles or parallax mapping; they said they'd add it in a future update.
I would recommend buying it either way however because it's just way more powerful X9 out of the box.
5-You can do good stuff with X9, but in order for it to compete with x10 in terms of visuals, you'd have to download a 3rd party mod for it. Like I said, X10 is just way more powerful out of the box.
H.K.