Ill try and answer some (due to workload here).
I take all GoPro files and Optimize using FCPX.
I wouldnt say its fool-proof cause Ive heard others having issues here and there.
If you really have to, use Compressor and output to ProRes HQ.
Now to move the project, its best to be on an external drive drive this way your Final Cut Pro Events and Final Cut Pro Projects are intact.
Once you open FCPX with that external attached, the projects will populate in the Projects list within FCPX.
If you’re not using an external, I wouldnt suggest any other option to moving your files.
Burning on a DVD or BD-ROM is the other options but dependent on your project/events size.
Splitting it up on multiple DVDs is a pain 😛
You will find both folders in your Documents folder if you’re not using an external drive.