Simple. If I work on one of my own mod on one computer, can i bring it up via the creation kit on another? I know you can load up mods you have placed on the workshop and edit those. Is it possible without uploading to the workshop?

Just copy the files to a flash drive or something. Other than that, no. There is no (longer) any built in version control with the CK.

If a plugin and its resources (if any) are present, it'll be operable on any PC.

Either that or download "Dropbox". It creates a folder on your hard drive, and uploads everything in that folder to your cloud account. Just save your .esp file in the drop box folder, and you can access it from a different computer.

Wouldn't you need Skyrim installed on the computer as well since it has to load the skyrim.esp?

Except you also need the entire scripts folder, not just the ESP or any scripts on your items won't work.