Vibration has nothing to do per se with the type of engine,and a lot to do with the balancing of moving engine parts.Overheating of engines also has nothing to do with the type of engines.But engines without forced air cooling regardless of type are obviously more prone to overheat at low speeds such as climbing hills..That the HT engines without cooling fans happen to be 2 strokes is incidental.Two strokes have higher specific output, (HP/liter),worse fuel economy and a louder more high pitched exhaust note.They are also a lot simpler,lacking valve gear and attendent problems.There are fewer things to go wrong.They put higher demands on the ignition system (twice as many plug firings) and are consequently more prone to misfire at high rpm.Having to mix oil is a bit of a nuisance,if you forget or let the engine run till it runs out of fuel you may be in for trouble due to lack of cylinder lubrication.(piston seizing)