The item to be pickled will designate the temperature of the brine to be applied. Sturdier items require longer exposure to heat. As a rule of thumb items which are to be eaten raw are to go into cold brine, items needing cooking go into hot. This decision will also be based on the desired finished texture of the item — the softer the result, the longer the exposure to heat etc.
For sweet pickle, use brown sugar and twice the amount. Of course, seasonings can change with intended use as well.