I think you need to move this question to the video thread, but what do you mean by "my computer must not lag at all because it will have running, and quick action going on"?

If the computer is capable of capturing the footage at full frame and your editing software can handle it, I'm not sure what the problem is here.

As far as the video camera. I would go down to the store and hold them in my hand. For $300, I doubt you could find a 3CCD camera, but you can find quality in Canon, Panasonic and JVC. I personally have a Samsung that I've been very happy with and when the on switch broke they didn't just fix it, they sent me an upgraded camera.

On the other hand, I know a guy who bought a DVD cam and he's not crazy about how the footage comes out. I don't have extensive experience with these, so I expect other people to chime in on the quality you can expect. The advantage of these is that you have a prepared dvd when you finish shooting. But if you want to edit, I'd go with tape.