wrote:
What are the kit or plans built planes that people use for aerobatics?

The choice of a bipe aerobatic airplane that you can build and the
ramifications involved with the decision on which aircraft to pick is a
subject way too complicated for a simple thread here on the forum.
Without knowing your skill levels both flying wise and as a builder, and
assuming you might be at the novice end of the scale (no offense
implied; just picking the best scenario from which to advise you)
A Pitts can be a real handful for a novice and some others like the
Skybolt can be a handful for a novice builder.
My recommendation would be to consult with EAA initially and possibly
consider building an AcroSport. Paul Poberezny designed this plane and
he did that with the novice builder in mind. The plans are written in
plain English and in easy to understand terms. A lot of beginning
builders have built the AcroSport and were happy with its performance.
I believe you can now build it with either the M6 or a symmetrical wing
if you like inverted stuff.
There are several engine choices as well depending on your pocketbook.
This is just a general answer for you of course, and my suggestion to
contact EAA is a sound one. For someone considering building a plane of
any kind, EAA is a priceless resource whose value can't be calculated.
Lots of luck whatever you do.

--
Dudley Henriques