The best option is to have a bike that doesn't wobble at speed. On a road bike, there are many bikes which are stable at upwards of 60 mph, and on an MTB, it should be similarly stable, although it is unlikely you will ever ride it at that speed.
Speed wobble is caused by an excessive amount of movement between the rider interface, which is in this case the handlebar, and the wheel. That movement can be in the bar/stem, headset, fork, or wheel.
It is a sign of a poorly spec'd bike at best, and possibly of a poorly designed frame.
Training for methods of falling safely is not a bad idea, as at some point you're pretty much guaranteed to fall, but avoiding falls by riding safe equipment is better.
Avoiding impact with your head or spine are the priorities in a crash. For that reason, sliding the bike out is our best option, however painful it might be. Looping out a wheelie is not a good option unless you're confident of staying on your feet, and you can't be confident enough to risk that.
Going over the bars is a movie stunt that isn't likely to end before ou plant your face in the ground. Repeat, head contact bad.
There is no safe way to crash. Ride safe equipment, and avoid crashing where possible, and be ready to suffer if you can't avoid the crash.