My version of floating thumb is just switching between anchoring strings (E and A on a four string) when you have to play patterns/whatever out of a three string range, so I'm just swapping anchors, not completely floating. To be honest I've skipped the floating thing for 4 finger technique which I'm working on at the moment. I've found it really is effortlessly efficient if you can get with it, both techniques need a more 'rigid' wrist action to get more attack on the string due to lack of anchor, it's not an easy technique to get down imo, if you've recently started it is tricky. If I had to choose I'd go straight to 4 finger (being thumb, index, middle and ring, the hair band on the headstock end of things helps muting a little. Imo having that technique down is the way forward for me to get more fluid.
I should add that my 4 finger works from thumb, ring, middle, index, I find the hand motion more natural this way, if you grip something your fingers seem to lead from the ring, up through the rest, so approaching 4 finger I lead with the thumb to ring and back, sometimes lead with the ring finger? Just a thought on 4. there are a few different ways to approach.