It has been a bit of an inconvenience whenever I would scan a single file as it would take forever to load the virus signature database.
When this process is happening, what is it really doing? Is it loading into RAM or what?

Not asking for something too specific here, but what I am getting at is that if it is being loaded into RAM and then 'goes away' when you are done scanning,
is there a way to remain loaded in RAM until it is needed again and executed a lot faster? Or regarding the possibility that it is being loaded into RAM,
can I somehow have the database directly loaded onto a swap file on a USB and then keep it loaded on that?

Edit: Okay so while the main problem is keeping the signatures loaded and ready for use whenever, the originating problem with it loading is that it's very heavy on the CPU. Is there any way of minimizing that amount of stress while also loading faster? I mean this isn't about deselecting file extensions from a list. It's just the efficiency to scan 1 item.

Yes, ClamWin loads the virus signature database(s) before each scan. It uses the scan engine and virus signatures provided by the Clam AV project for Linux. The ClamWin developers prepare a Windows port from the Linux source code. The developers change very little from the Linux original code in their Windows port. Clam AV was/is developed to be used by Linux email servers, for which speed was/is not important. We will have to live with this until/unless ClamWin comes out with a more Windows-specific version. I do not see this happening without a professional programmer(s) devoting some time to the free ClamWin project.

Because of this (and other) limitations, the ClamWin developers advise using ClamWin as a backup/2nd opinion scanner to a real-time scanner for Windows. It still works pretty well in that role.

Thanks for using ClamWin.

Regards,