Spot on

It's all about winning the collision, winning the wrestle and winning the ground. Every RL player is drilled 'first man high' to wrap up the ball, many coaches increasingly prefer the first two men high, and third to take the legs/hips. Win the process and slow it down.

If you tackle low round the hips you're not only risking an offload, you're not going to win the collision or ground (there would be no wrestle) and the attacker can get a very quick play the ball while your defensive line is still getting back, allowing the attacking side to get a roll-on.

Winning the entire process slows the attacking team down and allows your defensive line to get back and set, an perhaps even a moment's rest. There are also techniques in getting off the floored attacker that slow things down further.

In RU you make the tackle (to be fair, they are generally very good at 'textbook' rugby tackles), and take the man to ground where you can contest possession.

Regarding a smaller person tackling a bigger guy one on one, as has bn said, you have to go around the lower stomach or hips area, and then either try and get hold of one of the lower part of one of the legs, or, try and drag him/her down, which I don't like, as it can cause injury to the ball carrier, seeing tacklers push their bodies against the legs of the ball carrier, as I said, don't like that, as they sometimes fall on their legs. But adrenalin flowing and players are obviously desperate to bring he ball carrier down. Phil Gould was going on about this a few yrs ago, saying it's dangerous going for the legs, this for obvious reasons, and that the older generation keep going on about players should be tackling around the legs.

But IMO players should be allowed to stay on the ball carrier for longer than they are, especially if it's a good legs tackle, as some ppl do occasionally tackle around the legs, or slide down a you know. Also I'd have teams going back 8m instead of 10, but defences can't encroach until the ball has cleared the ruck, I'm fine with slower rucks, in fact I want slower rucks in RL. J Roby should never be allowed to churn up the meters that he does.

Stiff forearm. Go for the head.