Without proper position, you will be off balanced. Proper position comes from performing the first set accurately in front of a mirror. Sensitivity to force comes next. This comes over a long period of time from slow sticking hands practice. Timing comes next.
Power comes last.
Speed comes before power. In fighting, don't trade punches with your opponent, worry about your defense first. Always travel the shortest distance which is the straight center line. The opponent can start first but we get there sooner. Wing Chun is sneaky.