In most cases, not all, the mechanics that best create improved velocity are the same mechanics that create improved control.
i think people need to understand one thing in all these "how important is velocity" discussions. There are pitchers that throw low 80s that are wild. There are pitchers that throw mid 90s that are wild. There are pitchers that throw low 80s that have outstanding control, good off speed pitches and good movement. And there are pitchers that throw in the mId 90s that have outstanding control, good off speed pitches and good movement.
Based on the above, how important is velocity? Also, it's not always the fastball velocity. The high 80s slider is harder to hit than the high 70s slider if both do the same thing. Same goes for the change up. If two change ups do exactly the same thing and can be thrown to the same location with the same deception... The 85 mph CH, is harder to hit (or lay off of) than the 70 mph CH.
If two pitches are equal (Do the same thing) the hitter has more time to react to the slower pitch. In other words, hitters are more likely to chase pitches when behind in the count on the higher velocity.
For some reason, some people seem to think those that throw with good velocity have bad control And those with less velocity have great control. I do think most pitchers capable of peaking at 97 max will be better pitchers at around 93-94. Also think most pitchers that can max out at 82 will be better at 78-79.
Velocity is not everything, especially if everything else is missing. But no one can be a good pitcher when everything else is missing. The level of play often dictates how important velocity is. Both the hard throwers and soft tossers can be successful In high school if they can throw strikes. Then in college only the very most talented among those that lack velocity see success. Then in professional baseball even fewer low velocity guys that are successful. Those that are are extremely talented. Then in the Major Leagues it takes a lot more than velocity and control. Because nearly everyone that ever makes it that far can throw in the 90s. And many who can throw very hard never do make it.
Bottom line... Pitchers who have excellent command of two or three quality pitches stand out at any velocity. So how important is velocity? We have all seen the extremely hard thrower that throws straight fastballs and can't throw a strike. That's not good enough to be successful. But what about the guy that throws live moving low 90s fastballs with good command. Everything is important when it comes to pitching.
One last thing... I understand when people talk about the difference between throwers and pitchers. But isn't everyone a thrower before they become a pitcher? And usually isn't it the better throwers that become the best pitchers? I can't think of anything more important to a pitcher than his ability to "Throw" a baseball. That is where it all starts.
BTW, I really enjoy watching a great pitcher dominate a game whether he is throwing 80 or 100 mph. In fact, the guy throwing 80 is the most fun to watch, because he has to be closer to perfect. Still the ceiling is higher for the hard thrower.
A couple years ago two UCLA pitchers were picked early in the draft. Maybe not a great example because they both threw hard. Many thought they were picked in the wrong order based on what they did in college. I was very much on the side of the Pirates Who had the first overall pick. But I talked to some with MLB GM experience who said the other guy was better. My argument was that the guy they liked best had a ceiling of being a very good Major League pitcher. The guy I liked best had a ceiling of being one of the very best pitchers that ever lived. I still believe that is possible, but time will tell.