While you're still learning, high degree of float makes it "harder" to unclip, in the sense that moving your heel outward is not a natural motion (yet). More float means that you have to rotate more before the cleat will release.

But once you're used to the unclipping motion, it shouldn't be more difficult.

In general, high float is more popular for road, because rides tend to be longer, your body positioning is relatively stable, and you want to give your knee/foot positioning the flexibility to shift around a bit. Low float is more popular for MTB, because you're often out of your seat and jumping over things, and you want your feet to be more glued to the pedals.