I know CPU and GPU speed are important for rendering and editing videos. My question is: is CPU speed always important for uploading a youtube video? and actually how much important? I've searched on the web to find this specific question's answer but I wasn't satisfied.
Sending your files to YouTube (once rendered and or exported) will be down to the upload speed of your internet service provide (ISP) / Broadband supplier. The faster the upload speed, the faster it can get to the YouTube servers for processing.
So the answer to the question is no, but there are other factors involved like those mentioned above.