Hi Vilde,
I switched from Vmware to Qemu/KVM, probably 6 or 7 years ago now. The libvirt documentation (or maybe qemu documentation) said I could convert my vmware .vdk file to a qemu image, but I could not make it work, and simply reinstalled Win 8 to the virtual scsi disk with Virt Manager. I later bought a Win 10 license and installed that on the virtual drive.
AFAIK, you CANNOT copy and paste directly between the host and guest (If anyone knows how to do that, I want to see how to do it). But the host has an "Attach/Rlease" USB device menu item, so you can copy data to a thumb drive, then eject it from the linux host, plug it into a different USB port, and connect it to the VM and Windows will see it.
Yes, virtual optical drive can be connected to the guest.
I haven't tried to run the guest with no network, but I do not know why that would not be possible. Just don't install the virtual network device, and there will be no network (I assume).
Hope this helps.
NOTE: You'll want the Virtio Windows drivers as per this:
https://www.linux-kvm.org/page/WindowsGuestDrivers/Download_DriversEDIT: I think you might be able to set up the host and guest on a samba network and do file sharing that way. Too much pain for me to think about ....