All of the ones you mentioned are very good float planes. The Calmato and 4* are semi-symmetrical, so less aerobatic, and the Super Sport has a higher wing loading than the Tiger.

Don't worry about the wing mounted servos, unless you are flying from salt water, the splashes won't hurt them. It you want to be sure no water gets into the wing you can make a small shield over the servo arm slots that is open at the rear. They sell them for use on sailplanes.

Jim