And adding to what's been said, the main strategy in rugby is very similar to a traditional football running approach, except that play doesn't stop so it happens a lot faster. Basically, using the inside plays to set up an outside overload.
In football, you pound the ball up the middle and start to suck the LBs in and then bounce it outside or pass deep. In rugby, you use your forwards and centers to run inside a few times and hope to suck the defenders in, making them cheat inside and over-commit to tackles and rucks, and when they do, they won't leave enough defenders covering the outside, so that's when you pass it off and hope to get it wide fast.
Most scoring plays in rugby come from such overloads or missed tackles.