The "lighter version" only lets you add one camera, so you definitely want the full license. Since you have a full license already you can get more for half price if you ask the developer.
It can be installed on any drive, it doesn't have to be drive C.
Assuming the new build will be on the same LAN, you can do a registry export on the first machine, copy the exported file to the new machine, and import it there. When I do something like that, I use
Blue Iris Update Helper (BiUpdateHelper) to create the registry backup, as this produces a human-readable text file (
Blue Iris's built-in settings export does not). Then with a text editor I strip out the license information so that when I load the backup onto another machine I do not screw up the registration.
You also need to deal with any differences in file system layouts, including where the web server root directory is, where the clip database, clips, and alerts are stored, and change the storage limits to match the new hardware. You can do all of this through the Blue Iris GUI after you've restored the backup from another system.
It is perhaps more time-consuming but you can also import/export each camera's settings individually.
