Restore macOS factory settings for FusionDrive (diskutil list shows more than a dozen disks with little space)

Hello Community,

Ok, I am probably not the guy that should extensively use the terminal. But I managed to create a fusion drive with a bootcamp partition when I bought the iMac that worked very well. Now I want to sell my iMac and have deleted/formatted the disks to erase any data, and to reinstall macOS. I have also successfully merged the disks. Now, when I enter diskutil list, I get disk0 to disk16.

• Disk0 is the OS X base system.
• Disk2 through Disk13 are disks with variable but very small sizes (524KB to 6.3MB).
• Disk14 is 121GB physical (I assume the SSD part of the FusionDrive).
• Disk15 is 2TB physical (I assume the normal disk part of the FusionDrive).
• Disk16 is 2.1TB virtual disk

(See screenshot below)

Also, after successfully installing macOS, I can boot in macOS but do not see any hard disks (no user folder, i.e. no Documents, etc.). Now, I would like to reset everything to factory settings so that the buyer gets a fresh clean start. My questions:

• what are all these small disks? Can they be deleted? If so how they can be deleted?
• can I these small disks be merged to the FusionDrive?
• can the disks be renamed from disk0 to disk2?

Basically I want to restore the factory settings of the disk setup and reinstall macOS. I definitely do not know how to do this, even after searching the whole web! Therefore, any inputs would be very much appreciated. Thanks a bunch!

Cheers, stefan