Your computer isn't that bad. If you lag while playing minecraft, I would reccomend downloading optifine. It is a mod that increase your FPS by quite a bit. That mod alone will give you a nice FPS boost but if that isn't enough, there are many options that come with it and you can even increase your FPS more. As for recording, I would use Fraps, as that is what I use and It is the best. It is easy to setup and use. Good luck with your channel!