It's 4 jumps cos so tricks in all four directions (right, left, sw right, sw left) can be done. Also three jumps just feels short, the X Games feels like it should be about the great 'murican tradition of making things big.
Also definitely three runs, It'd encourage people to go for more crazy stuff because they'd have more chances to throw down.
Grabs - I'd put grabs that help rotation (the absurdly high mute/ tweaked out true tail) on the same level as a safety, or even no grab at all. Grabs are to look good and show your confidence with the rotation, not to help you add a 180.
Jumps (50%) - Different axis. Corks, normal spins and flats/rodeos are pretty much the only type of rotation we see. I'd like to see more than that, Henrik can do the lobster flip (dub bio/flat 14), that would certainly be an event winner with me as judge (along with the rest of Henriks run, which would probably include a nose butter triple, switch butter 10 and right butter 12). I'd also include other types of jump, like maybe a hip where you have the choice of going to either side or over the top. Maybe a feature like the Breck park setup in Sunny, where you have a small half pipe with jumps into or over it.
Rails (50%) - Same value as jumps. Often you feel like 'easy', sometimes not even edit worthy, tricks are being thrown on rails just so the riders can focus on the jumps. If simple rail tricks (90 on, 270 out like tricks) earn you only 10 points, then no matter how good your jump section you can only score 60. Creativity is awarded in the rails. There is no criteria for creativity, because if there was a list of 'creative' things you could do they wouldn't be creative. Doing things that the feature isn't intended to be used for, and that other guys aren't doing would be creative.