Clouds stay aloft for the same reason that dust motes floating around, also heavier than air: air drafts push them around. Is Einstein's theory of general relativity correct?
To this end, is it possible to have a hotdog-shaped planet, or will rotational and orbital forces (and others? The main reason is that astronomical objects are usually formed by smaller pieces coming together.
Initially, very small stuff (dust size) sticks together by colliding and since this is a random process, is just as likely to stick a little piece on any part of a larger piece with which it collides; therefore the initial "seeds" tend to be roughly spherical.
You would likely fail because gravity would cause it to collapse under its own weight.
The earth is actually slightly oblate, that is fatter at the equator than the poles, because it is rotating and the centrifugal force pulls it out at the equator.
In addition to the Bernoulli effect to which you refer, the "angle of attack" is also important.