Hi Doug. Too large a topic to cover well in one post...
To answer ur question about whether or not the top of the plant being eat off affects the root The answer is.... It depends. Lol
First year plants that get eaten before mid summer are toast. Kiss them good bye. You see the growth bud for next year is usually formed \"but not fully developed\" by mid summer. Older plants may have enough energy stored in the root to develop next years bud without a top, but first year plants never do.
Even older plants will eventually die if they are repeatedly eaten off early in the growing season. If they aren't eaten off until late July, or early August, I really don't believe it hurts them at all other than slowing down the root growth...
About protection from predation....
Although it wont help with insect or slugs I believe that tree tops may be the best protection from deer, turkeys and two legged predators. Just cut and drag limbs from recently fallen trees and stack up in SMALL brush piles right on top of your patch. You want it thick enough to deter animals, but not so thick to completely block out the sunlight...
I have assumed that you are wanting to grow some version of wild simulated... lol (A whole other discussion).... IF you help it too much along the way then you will end up with cultivated looking roots...
Your objective is what will determine how much you should help it out....