RE: First aerobatic machine: what?
The stiks, like the Sweet Stick or Ugly Stick are very good advanced trainers/ aerobats. They offer low landing speeds. Stiks aren't as popular as they were in the 80's and early 90's. thats a shame really. They are excellent 2nd or 3rd planes. One hint. Dihedral kills thier performance. I would recommend zero dihedral. That way the plane stays in the attitude you place it and has no tendency to roll level at all.
The Super Sportser is a great intermidiate aerobatic airplane. It is capable of high and low speeds and is very responsive through out the speed range. It might seem a little hot at first and difficult to slow down, but it will actually fly great at low speeds in the hands of an experienced pilot. that might be just a little too hot for you.
Many people rant and rave about 4 Star aircraft. I test flew one a few years ago and was not impressed. Although it might be fun for you now, it won't be next year. The plane is much more limited. However, it appears to be easy to build. And is probably the tamest of the planes I have mentioned.
Profile catagory ? Well, some planes are just that. Imagine you cut the side view of an airplane out of a piece of wood. That would be your fuselage. The wing is normal, but the fuselage has no "inside". Equipment is either placed in the wing center section or strapped to the fuselage side. These are extremely easy to build. They are cheaper. They are generally lighter and offer greater performance due to their light weight. But they don't look as nice.