Like with all trainers you will have some good Amish trainers and some bad ones. All the horses that I've worked with have been Amish trained and they've all been very well trained, some of them didn't have friendly personalities, but that was more based off of the horse than the training because, as I said above, they were very well trained.
And yes, most horses will pick up the personality of one, if not both, of their parents. My mare's personality is her sire's personality (thankfully). But it's not always a sure thing, other variables will factor into a horse's personality.
"And somewhere in the northwoods darkness a creature walks upright. And the best advice you may ever get is: Don't go out at night..."