Getting and installing CargOS
The regular image is intended for a manual installation with persistent storage.
The noinst image does not include the bootstrap tarball which means it can only use persistent storage configured by the regular installer. It is mainly used for booting over PXE, USB, ISO or whatever to use an already configured system where the bootstrap tarball is not needed.
The cloud images will do an automated install without asking any questions and by booting that image you will overwrite your first disk. No questions asked. It will then try to get the cloud-config data from the generic sources (cdrom, iso) and use them.