If two runners of equal capacity (VO2 Max) enter a race, the runner with the greater running economy will use less oxygen and therefore less energy, and unsurprisingly will almost certainly win the race.
It is important to note that the presence of speed, does not necessarily mean that a runner is economical. Equally the absence of speed, does not necessarily mean that a runner is un-economical.
There are a number of factors that affect running economy including, but not limited to metabolic adaptations within the muscle, the ability of the muscles to store and release elastic energy, strength training, altitude training, gear choice and more efficient running mechanics. An improvement in running mechanics, better known as technique leads to less energy wasted on factors such as braking forces and excessive vertical oscillation.
We know that running technique is one of the factors that effects running economy. We also know that running economy is the decisive factor when it comes to splitting two runners of equal ability (VO2 Max). Therefore, in answer to the question of whether technique matters, the answer is that yes, technique definitely matters.
Unfortunately, there is no gold standard when it comes to technique, though there are some fundamentals that should apply to the way that runners move. Each individuals technique will vary depending on (but not limited to) anatomy, biomechanics and personal history.
All runners can and should be looking to improve their running technique, and in turn their running economy. Denis Kimetto holds the marathon world record in 2:02:57. I am very confident that he is constantly trying to become more economical.
Conley, D. L. and G. Krahenbuhl. 1980. Running economy and distance running performance of highly trained athletes. Med. Sci. Sports Exerc.
Saunders, P. U., Pyne, D. B., Telford, R. D., and Hawley, J. A. 2004. Factors affecting running economy in trained distance runners. Sports Medicine.