I've enjoyed reading these responses, which have pretty much confirmed what I suspected. It's all personal taste. One person's unruly mess is another person's exciting natural jungle. One person's trimmed arrangement is another person's contrived fabrication. There are really no right or wrongs.
As an example, before going away for two weeks, I set up my tanks with some medium sized Water Sprites set up on both sides of my tank -- groomed and landscaped so as to be pleasing to the eye. Quite arranged. I returned after two weeks to find that my two Sprite bushes, as expected, had grown into huge monsters -- with lots of nice lovely green growth, but also lots of "out of place" stems and dripping roots. Time for a haircut. The first bush I yanked out, taking a handful of substrate with it and filling the water with debris. What a mess. I trimmed the pieces and replanted. Not bad. The second bush I left in placed, removed most of the dangling roots, trimmed back certain stems - much less of a mess and the end result was more natural looking. But this trimming took a LONG time to do. And if it becomes a chore, the less likely you are to maintain it. Lesson for me: no need to completely butcher your plants if you like how they look.
I think the key is to have fun and go with what you like, not what the books say. Sprite might be regarded as a weed and a lesser, cheap plant but hey if you want to have a tank full of Sprite, go for it. Haha.
If I wanted an arrangement of locked perfection, I would have stayed with plastic plants.
Change is part of the planted tank experience.