Undoubtedly more questions to follow. Float is good. You want float. The first generation of clipless pedals locked your foot into a fixed position relative to the pedal. The amount of float is indicated in degrees, and depending on the pedal you choose, can be as little as 4 deg or as much as 35 deg.
Some pedals offer variable release tension.
This is a separate feature. Road shoes are designed for riding, not for walking. I've had the pleasure of walking a couple miles in my road cleats. Not much fun. The thing you need to look out for is the drilling pattern in the shoe.