L4 and L5 are unstable unless there is an extreme, as in many orders of magnitude, difference in the masses involved.

At equal mass the separation increases until they are all equidistant from each other assuming a completely circular orbit.

That applies to a small body with two large ones, not three similarly sized planets.

Ah, you are correct.

Is there any statically stable shared orbit for planets though? The first wobble and they start accelerating toward each other don't they?