It's probably about time someone introduced a little science into this discussion. And the science that's been done on this question (see links below) fails to confirm that self-monitored adjustments to running form, including the usual cues (arm carriage and foot-strike), increase the key variable in distance runner performance: physiological economy. Some research even shows that attempts to "improve" form via self-monitoring actually reduce economy.
https://runningmagazine.ca/sections/training/heel-strikers-can-relax-gait-retraining-is-not-warranted/
https://sportsscientists.com/2007/10/pose-running-reduces-running-economy/
This does not mean that there is no link between biomechanics and physiological economy. It just calls into question claims that an athlete can actually improve economy through conscious self-monitoring.
One only has to watch an infant progress from standing, to walking, to running-- then, if he/she takes up competitive running-- to see that we all tend to develop a smoother, "quieter" running action with increased maturity and experience (but all the while retaining many of the basic "signature" elements of form seen in early childhood). When it comes to movements as natural and basic as running, it has to be the central nervous system itself, responding to the biomechanical determinants of the individual (height, relative limb length, tension in the connective tissues, and a thousand other variables) that determines what we eventually see when someone runs. And nothing is more basic to human behaviour than running. Unlike the higher level, skill-based activities we're capable of, a human being can and will learn to run without ever having seen another human being do it, let alone receive deliberate instruction.
So, yes, faster runners tend to have better adapted running form than slower runners. But they also tend to be leaner, lighter, and a bit less flexible than slower runners. The question: How did they get this way, and can slower runners be "taught" to be faster, including to have a better adapted way of moving? And the answer is largely that faster runners were born with a greater predisposition to running, but also that they did and do a lot more of it than slower runners (and proficiency in distance running correlates better to total miles run than any other variable-- it's the sport in which training plays the greatest role relative to natural aptitude).
Encouraging a slower runner to self-consciously adjust their form to look more like faster runners regardless of how much running they have done, or their basic aptitude for the sport, is much more likely to lead to frustration and failure than it is to lead to improvement. For one thing, it entails the assumption that some observer with no proven, systematic basis determining optimal running form (either in general, or for that individual) is a better guide to optimal running form than the runner's own central nervous system when it is given the simple, primordial command: "run".
If you want optimal running form, you can only get it for your personal set of biomechanical givens, and you can get it most quickly through sending the simple "run" command to your CNS as often as you can. It'll find the line of least resistance. You might also want to do some basic strength work, to make up for the ways in which your modern lifestyle has made to you weak in the places you need to be strong in order to run without dysfunction. But running itself creates a lot of movement-specific strength too (runners have far stronger feet and calves than non-runners, even without strength work). Don't take the enjoyment out of your running by thinking that you run "wrong", and by expending precious psychic resources trying to adhere to some movement template that doesn't exist. Run more and get strong. That's all any of us can do.