you would mix up your punching on the heavy bag with light shots and heavy hitts. through repetitioin you will gain speed and power. but you can also hit the weights or medicine ball, or kettlebels to help tone to help create power
This:good If you have a 40 lb. bag, it should jolt with just jabs but you won't get the same effect on a 100 lb. bag. If you're making a 100 lb. bag jolt, you're smacking with some power.
Nope. Just means you're punching it correctly with some force. Hitting a person who's trying to avoid it and hit you is an entirely different matter. You won't be as set, you'll have to sacrifice power for speed, you'll get tired, your technique will deteriorate, etc