I generally use critically balanced baits popped up off the eye of the hook.
I find that it is a very good presentation for most varieties of lake beds. I suppose, for peace of mind, knowing that if you have cast onto a small patch of silkweed or whatever weed, your bait wont sink into it, and ultimately ruin your rig presentation. Neither will it stand "too tall" on a clear lake bed and appear unnatural.
As for the bait wafting around, I have found that as long as your rig is designed to allow for this, I have found this a positive. I have noticed that most wary carp will actually try and move a bait before actually swallowing it. Sometimes, I have seen them use their fins to create a disturbance or they will suck and blow (without inhaling the bait) just to see how the bait will act. They may do this a few times, leaving the bait and coming back later to try again before they are totally confident. I find sometimes that a bait straight out of the bag will act differently to the other freebies sraight out of the bag because of the hook etc that makes your hookbait heavier and therefore act differently to the rest of the freebies.
I think the most important factor though in effectiveness of the presentation is massively controlled by the baiting situation which you have created.
I think it depends on the:
1/ quantity of freebaits
2/ size of freebaits
3/ location of freebaits in relation to your hookbait.