1. You can do clips in either one. I import the footage into Premiere, drag and drop it into the timeline in Premiere and cut and paste there, but you can also do it in Vdub. But I don't really have any experience with that. But it should have something in the guides with it or someone else can help with that. (Me & VDub aren't really on speaking terms right now. Great program, I just came out of a bad argument with it. lol.)
2. Premiere does in fact come preloaded with effects and transitions and stuff. Basic to mid ones, but good enough to get a pretty decent vid out.
3. After Effects lets you do more advanced effects than Premiere. (But I've never actually worked with it, so I can't answer much in that dept)
4. Yes, it does. Especially if you don't have After Effects and want to do effects that you can't normally do in Premiere or you just want to put some kind of overlay (text, shapes, interesting borders, etc) on the vid. It can also help you with lip syncing. (like covering and fixing unsyncs and lip flap where you're having trouble getting it to look right.)
Hopefully this helps at least a little. If not, hopefully someone more advanced than I can come in a give a better answer. lol. I'm just not always good at describing stuff.
