Seems like you might be misunderstanding how PD's media library works.

It's a virtual library, not a physical one, so when you "import" a clip you're simply adding a placeholder to the original clip. There is no additional copy made or stored anywhere, certainly not in the project file (.PDS). Having 0 or 100 clips in the media library makes no difference in the size of the project file.

However, when you use Pack Project Materials, PD does make copies of all timeline clips (not all clips in the media library) and places them in the packed project folder so they are all available when opening the project on another computer.

This brings up the 3rd point, which is that if you're copying just the PDS files into your archive, you aren't bringing any of the media clips they're using along with them. You'll be in for a nasty surprise if you try to open that project but have already deleted the required media clips from their current folders.

If you use Pack Project Materials for each project you'll avoid this problem and can then delete the original media clips without issue.

Finally, if you will only ever use 10 sec from that huge GoPro clip and want to save only the usable content in your packed project folder, simply produce the desired section (ideally using SVRT so there is no re-encoding) and place the produced clip on the timeline in place of the original trimmed clip. You can then delete the original clip or remove it from the media library, if desired.