ntti, I suffered a pretty severe back injury 20 years ago (bed ridden for a few months, over a year until I could walk normally again). I can't tell you whether or not my personal experience is representative of that of others, but I can tell you that moving my back quickly frightens me still.
Personal Bias
Your back issue clouds the issue of your view of "Speed (Power) Training"; understandably so.
For someone with your situation, "Speed Training" may not be effective.
I think speed as we use it in kettlebell ballistics is a safe and effective thing for many people - the weight is much lighter, the rep count generally higher, and the net effect different, I think.
Speed Training with Traditional Exercises
The application of "Speed Training" with Traditional Exercise is that same as with Kettlebell Speed Exercises.
Speed Training Percentage with Traditional Exercises is defined as load of 10 to 40% of 1 Repetition Max, with 30% of 1 Repetition Max usually being the most effective. Source: S
upertraining/Siff and Verkhoshansky.
Thus, the weight is "Much lighter", as with "Kettlebell Ballistics".
Power Training Percentages
Power is developed in Traditional Exercises (Squats, Bench Press, Deadlift, etc) with load of 48 to 63% of 1 Repetition Max.
Thus, the weight is still "Much lighter" (falling into a Moderate Loaded Movement). Due to the moderate load for the Power Movement it should allow all lifters to adhere to technique.
It is mandatory for any lifter unable to perform a movement with any training load percentage to decrease the load; develop technique with that Training Load Percentage. Then the exercise load can be increased.
Speed, Power and Strength Training Repetition Range
Speed, Power and Strength Training employ the same Repetition Rage, 1 - 6 Repetition.
That due to the fact that Fast Twitch Type IIa and the "Super" Fast Type IIb/X fatigue in approximately 15 seconds.
A down gearing effect occurs the longer a high intensity movement is performed.
"Super" Fast Type IIb/x quickly are exhausted. Once that occurs, they downshift to the Fast Twitch Type IIa.
Once the Fast Twitch Type IIa fatigue; the Slow Twitch Type I Fiber perform the movement.
With that in said, you are correct in you assessment that...
"...Much lighter, the rep count generally higher, and the net effect different,..."
Lighter loads, with higher repetitions build and promote endurance rather than developing Speed, Power and/or Strength.
when I'm deadlifting a barbell, my focus is on pushing the floor away with my feet and moving my hips forward, and not about trying to do either of those things more quickly than what comes naturally to me.
The Conventional Deadlift Is A Pull, Not A Squat Press
I have posted research information on this site and others.
Research (Dr Tom McLaughlin) found that in a 1 Repetition Powerlifting Deadlift "Pull", the lower back initiates the drive off the floor. Additional research by other has confirmed McLaughlin's finding.
The Back initiates the drive off the floor, the Legs kick in. It is a "Bang-Bang" Sequence. It occurs so quickly that it is hard to recognize.
The traditional recommendation of, "Pushing the floor away..." amount to "Leg Pressing the weight off the floor.
With that said, the Legs/Quads are important in a Conventional Deadlift. That is why I recommend Auxiliary Deadlift Exercise include; Quarter Squats, Quart Step Ups, the Leg Press, the Hack Squat (as you have noted is a great Quad Exercise, Front Squats, etc.
Doing What Come Naturally
The caveat is that "Doing what come naturally" doesn't mean "Performing it correctly.
In working with a kid on his Good Morning Squatting Technique, he told me that it felt natural.
If you perform a movement incorrectly long enough, it will feel natural.
In correcting his form by working on his technique, he stated, "It didn't feel natural."
My reply was,
"Keep doing it until it does feel natural".
Sick months later, it his new improved technique felt natural, his Squat went up and his Deadlift, as well, since he wasn't beating the crap out of his back with a Heavy Good Morning Squat.
Take Home Message
1) Compensatory Acceleration: Speed/Power Training with Traditional Lifts (Squat, Bench Press, Deadlift) have documented research demonstrating they are a vital component in the development of Strength; pushing/pulling more weight up. Dr Zourdos', Dr Daniel Baker, Dr Jeff McBrides research is available on line.
The Westside Powerlifting Training Method has been around for close to 35 years. It provide definitive empirical data that demonstrates it works.
2) "...Speed and form aren't at odds...": As per Antti, both can and need to trained at the same time in some form or fashion, via Conjugate Training.
3) Your Bias: You're bias against Speed/Power Training is driven by your back issue. I have some understanding and empathy for you.
However, just because it doesn't work for you (for whatever reason) doesn't mean it is ineffective or productive for others.
Creatine does't work for me. I am a non-responder.
However, I endorse it because I've seen how effective it is for the majority who do use it.
Kenny Croxdale