TLDR: Smaller is more ideal
Well, Homo floresiensis were tiny, measuring only about 3 feet in height. They were not midgets or dwarfs, simply a much smaller version of Homo sapiens. In an alternate universe they very well have been the norm for our planet, but I think much of our size has to do with competing against predatory animals, which tend to be larger than their prey. If you had a non-meat eating race with only limited exposure to predators it could be smaller since it doesn't need to out-chase or fight for food, or defend itself.
Coincidentally, the Spartans were the fiercest and most efficient fighters of their age, and Greeks tend to be much smaller than Germans or Nordic based people. I mention this because weapons are what really blossomed technology through the ages. Being small has a lot of advantages as you need fewer resources to survive (less food, less material for clothing, smaller structures for housing, etc.). This means those same resources can be spread out over a greater number of people, which means more minds working to create new discoveries.
In summary, the smaller you are the more densely you can live, the less food you need, the lower the impact you have on the world... there's also a study that shows that shorter people live longer than taller people. This leads me to surmise that smaller is in many ways better, but due to circumstances of who won which war, population growth, etc., we are on the larger size these days. Our size has not affected our intelligence, and there's no current evidence that we would have had more/fewer technological advances had we evolved smaller.