As a rule...
Higher gauge (thinner) wire will "hot spot" more easily because it has more resistance per inch.
The number of wraps is completely determined by the resistance of the wire and the desired resistance of the completed coil ( and space limitations).
More wraps will give more vapor (but not necessarily more flavor) because it vaporizers a larger surface area of the wick (more
juice to vaporize).
Hot spots are the killer of any coil. If you have an area that gets hot dramatically faster than the rest...it's a hot spot and it will make the vape taste burnt. Tails of the coil are notorious for this; keep them as short as possible...like none at all, if you can.
Thicker
juice (i.e. high VG content) will always wick less than thinner juice. In some cases, you may want to thin it with a LITTLE alcohol (we're talking drops). And, when wicking is not optimal, hot spots cause more of a problem.
EDIT: Another prime hot spot maker is loose wraps. Essentially you want to make sure all of the resistance wire is touching something or it will turn into a hot spot and give you that burnt taste.