The important thing for how much speed and spin you get on the cue ball is how fast the stick is moving at the instant of tip-to-ball contact. The ratio of spin to speed is determined almost completely by how far off center the tip hits the ball. That's what physics tells us and what we see in practice.
There is no "strength" in this analysis. If a very strong person and one with less strength but better timing both get the stick moving at the same speed and achieve the same contact point, they will get pretty much the same results.
I totally agree that 25 mph is 25 mph.
It makes no sense, technically/physically to say "very fast, but not hard." I think you are referring to the "quality" of the draw. "Quality" is a technical term I got from a European Champion Artistic Billiards player. It means a high spin-to-speed ratio on the cue ball. This ratio is demonstrated in the Wagon Wheel Drill where the outbound angle of the cue ball is (or can be, if the cut angle is kept constant) determined entirely by the quality of the draw/follow.
The part in red, I'm not sure I understand completely. There is a drill (I'm thinking you posted it, maybe not) where you put the ob somewhere around the spot, and see how much draw you can get with the ob going as little distance as possible. The way I understand it, is this is achieved by high spin to forward force ratio. You want to hit with high speed, but little forward force. The more forward force (the harder you hit), the farther the ob will travel. So, you are saying this is not correct?