I am one of those people who obsesses over where a horse will break from (their gate position). When I seen that my derby pick (whom I've been following for about a year and a half now) Uncle Mo, got the 18th gate position I knew right away that he would be racing traffic the majority of the race, he is now out of the race -- so my back-up horse, Dialed In (with the 8th gate) will be breaking from pretty decent turf. This of course depends on all kinds of factors, like how he will break from the gate -- maybe he'll stumble, who knows, it is a horse race for a reason

One thing the some people may not realize (unless you follow horse racing), is that you can't just "drive" your horse all over the place, you can get disqualified for this. You have a "lane" that you stay in, and only move when it is safe/clear to do so -- just like driving a car on the highway! So if a horse breaks with a lot of traffic in front of him, he needs to make a lot of SAFE lane changes in order to get to the front of the pack.

As for holding the mane for coming out of the gate -- the majority of the horses breaking out of the gate aren't running, they're leaping out, and usually take one-two leaps up/forward to reach top speed, which happens very very fast you certainly want to be hanging on until the horse reaches running pace 

Horses Leaping Out of Gate