I am working off a 2TB SSD drive. I chose the "copy to" function in addition to the create optimized media and proxy media. Now that i see how large the optimized media files are I am wondering if the "original media" contents are necessary for 4k export? I ma already running out of disk space so would love to delete that folder if not necessary.
As Tom says, the Original Media folder is absolutely necessary.
There is no reason to create both optimized media and proxy media, that's a waste of drive space. If your hardware does not allow you to work with the original media in a smooth way and you don't have enough drive space to create optimized media, just create proxy media and work with these until you need to export. Then you simply switch to original media to export your project at the highest quality.
If you already have created Optimized and Proxy media for this project and you want to delete either the optimized or proxy media, you can do this right inside FCP X with the "File > Delete Generated Media" command. You can do this for the entire Library, or for specific Events in your Library. You NEVER should mess with folders or files inside the Library package using Finder, that is a recipe for disaster.
Thanks for the advice!! Followup question: If I want to do color work I still do not need optimized media? What's the purpose of even making it? Does FCPX work the slowest with original, second slowest with optimized and fastest with proxy?
The purpose of optimized media is to allow smoother editing playback on machines that cannot efficiently process the original media. While ProRes optimized media is much larger in file size, it is more efficient for your system to decode than some original media may be, especially highly compressed footage like h.264, so it provides this benefit when playing back and editing. Although it is relatively lossless in visual appearance, it is no better quality (and possible slightly less) than your original media. For color grading, if you can't use original media, then optimized would likely be better than proxy files to judge critical grades. In this case, you can switch the FCPX viewer to "better performance" while cutting, and then to "higher quality" when color grading - with original media if possible.