I tell you my direct experience with e-collars for training, not aversion, like in rattler proofing.
We had a top herding trainer, he had won the first cattle dog futurity, his dogs were top bred and extremely well trained.
He trained for years without e-collars, then when those were introduced, he started using them at times.
We had been training under him, I had done some puppy raising for him, he bred a few dogs a year and his working dogs were kennel dogs with house privileges.
Still, you can only raise so many puppies in a house, so I took the occasional one to get it started in household manners and basic obedience.
Serious herding training itself would not start until one turns on to herding and most do that between 6 months and a year.
I lost my bc I was using on our cattle and in herding trials.
I didnāt want another dog and one day he gave me one of his puppies.
I was training her in obedience and that new agility training stuff that was just starting then and she was a star at it.
She was herding well, attentive to the whistle for long distance work.
At that time he started using e-collars and wanted me to try for long distance work.
His idea was, if in training a dog is where it is not hearing the whistle, an e-collar could help.
I was hardheaded and didnāt want to, just no, set against it, not knowing better, but that has never stopped anyone from having an opinion, right?
He insisted his dogs were trained better when they didnāt get to not hear him and make mistakes.
So, I never did learn that one more way of training, to use that one tool, but now decades later realize it would have been fine, my dog would have been fine, used properly, as his dogs were.
I will still caution about e-collar use, as with any other tool, you need to know what you are doing or any can become abusive.