The phrase "soar off" is correct and usable in written English.
It is usually used to describe a bird or other flying animal taking off into the sky, such as in the sentence, "The eagle soared off into the clouds."
Seeing good shots soar off your driver is a rush.
It threatens to soar off into the incomprehensible, like an untethered helium balloon.
Some depart from traditional mandala patterns to soar off on their own, and it's hard to find dull examples.
Sometimes I was where I was, sometimes already at my destination, but never did I soar off into the distance".
The situation gives the playwright a chance to soar off into ostensibly poetic fancies involving celestial metaphors and spiritual mystery.
Of course, you'll point out, such transformations often depend on a dominant newcomer, like Ure, providing the momentum to soar off on a new course.
But when their mouths are shut, "Gravity" soars off to astonishing new cinematic territory.
Riders twisted and spun their bodies and motorcycles while soaring off metal and dirt ramps.
But it was worth it for that incredible feeling of soaring off a mountain.
By comparison, the buildings, though so humdrum, seem to be soaring off and up into notions of the ethereal.
Bob took his reward from my hand and then soared off in search of a pocket of warm air, which provides a lift to both bird and glider.
