Overclocking will make your phone faster at the expense of battery life, and perhaps making the processor die prematurely (i.e. making your phone stop working; this probably depends on the extent of overclocking, and probably shouldn't happen noticeably anyway. Probably still last a good few years). And the "cons" of rooting AFAIK are if you're not careful, a malicious app could mess up your phone and steal more info than a malicious app on a non-rooted phone (but if you root correctly, you should have to give permission to any app to "use" the root), and it probably voids your warranty.
Yeah, you would definitely void your warranty. Although you can easily reflash the original firmware and there's no way the repair guy can tell if your phone was ever rooted.
Anyway, rooting is pretty important when it comes to doing a lot of stuff such as taking phone screenshots or backing up app data. It's really recommended you do it, but yeah you have to be careful what you are doing. Don't go modifying system files without knowing what you are doing and don't download apps from dodgy places.
How much faster is it though like enough to be worth it?All im worried about is speed not full control and also i got my phone through a plan with phone insu on it would it do anything to that if say maybe i crack my screen and need to replace it through verizons phone insu ?
True but I think unless you cover your track properly the repair guy might notice your phone has been rooted at some point, especially if you have been changing some root files which should otherwise be inaccessible, and voids your warranty. Best to be safe.