I read something that said that if you have the majority of planets in the southern and eastern hemisphere of your chart, you have more freedom of will whereas if you have the majority of planets in the northern and western part of your chart, you have less freedom of will and more is decided on fate. How true is this?
Sounds like a paraphrase of something Steven Forrest wrote. But he didn't use the phrase "freedom of will." I think there's something being misconstrued here.
The eastern hemisphere is the "self" side of the chart. The western hemisphere is the "others" side. If the majority of planets are in the eastern hemisphere (houses 10-3), the native is likely to be a self starter and to have an "I make my own luck" attitude. This is someone who needs to do things by and for themselves, and will probably experience life as a series of choices, with what happens to them being determined by the choices they make.
If the majority of planets are in the western hemisphere (houses 4-9), the native is likely to need to collaborate with others in order to accomplish things, and likely to experience life more as what happens to them than what they choose. This is the person who will find that opportunities come their way rather than being consciously sought out, and when they do make choices, keenly sense the way their options are dependent on their circumstances.
The northern and southern hemisphere differences have to do with need for visibility or lack thereof. If the majority of your planets are above the horizon (southern hemisphere, houses 7-12), you're likely to want your personal accomplishments and milestones recognized by, and shared with, others. If the majority of your planets are below the horizon (northern hemisphere, houses 1-6), your accomplishments and milestones may be personally meaningful to you, but you don't feel much need to have them recognized and shared. Below the horizon is "in here," personal self, private. Above the horizon is "out there," visible, in the world.
So if you have a concentration of planets in houses 1-3, you get the combination of "self" and "personal" as a chart theme. And if you have a concentration of planets in house 7-10, "others" and "out in the world" are a chart theme. The southwest is the westest west, and the northeast is the eastest east. The other houses have more of a mixed theme.