I guess what determined the shapes as well as the planes in which these orbits are???? I mean, for example, why aren't all orbits in 1 plane?
After the planets were formed, their gravities balanced each others with respect to themselves and to the Sun.
If the orbits were all in one plane, then they would have collided with each other long time ago.
Everyone talks about gravity. That is confusing.
Let me explain.
Space is a fabric. Think of space like this and everything will start to make sense.
Imagine space is a rubber sheet stretched tight across a big trampoline. Ok? Now! All objects in space have mass. Some weigh a lot more than others.
If you put a 16 pound bowling ball in the middle of the rubber sheet, what happens? It sinks. It bends the rubber sheet. Imagine that bowling ball is our Sun.
Now put a marble, let's say Earth, on the rubber sheet. What happens? It automatically starts rolling to the heavy bowling ball which is bending the entire rubber sheet, or space. That is why Earth, in real life, revolves around the Sun because the Sun has bent space so much and our little Earth is "in the bend".
That is planetary gravity. Objects bending space.
Depending on a planets speed, mass, and where it resides in the "bend" of the Sun, that determines the shape of it's orbit.
When our solar system was formed a motion was set up and everything followed this motion and this is explained in Newton Laws of Motion. Then other forces influenced this motion (close gravitational fields), And further bumping and colliding of objects in the orbital planes of the planets further modified the orbits. The orbits are continuing to change today. Consider the Moon's orbit around the earth, it is moving further away.
The planets formed out of the disk surrounding the Sun in its early stages. This is the reason that the orbits of the planets lie in more or less the same plane. The orbits became circular when the proto-planets cleaned up space from left over comet like bodies.