So do you think the Speedplay's and float in general allow the foot to take a more "natural position" and then once you became used to how that felt you could set up the cleats to lock that in?
Yes. I think that is the phenomenon. What you think is 'natural' can change when you are actually out putting significant power to the pedals.
So what I did was gradually tighten the float adjustment screws until I could feel that I was pressing up against one side or the other more consistently while riding. I would back off the "touching side" and tighten up the "floating side" just a little bit on a succession of rides, until I just had it so "centered" that they were both clamped tight and there was no float.
maybe there people who are more sensitive or perceptive than I, who can set it correctly much faster. but this works for me.
Since I am already comfortable with the full-float of speedplays, the little extra float that I have during the tightening/centering process doesn't bother me, so I can still ride without thinking much about it. Just take a little screwdriver with you on a day when you are not worried about stopping once in a while. I don't even have to take off my shoes, just make the adjustments about a half turn at a time.