Is it SAFE not to use deck post concrete anchors?
I am unclear why you want to float the piers over the concrete. By using Simpson post anchors or equivalent, you can adjust the posts up and down, although typically not laterally. With fixed post attachments, you generally adjust the vertical position of the posts using shims.
I am not sure what code requires, but it is always a good idea to anchor the posts to the foundation in order to prevent movement of the deck due to wind, earthquake, or vehicle impact. This can be done with J bolts or post anchors. If you are concerned about not lining the posts up correctly with the deck joists, put the posts in first, then attach the joists later.