I can make bootable sticks in five minutes but if I copy a file of similar size to them is half an hour
This is the bit that interests me. Are you saying if you e.g. restore an ISO image, you can write to the USB a lot faster than when you copy files? If so, that would either point to a filesystem driver issue or an issue with the tool being used to copy files. Or something else interceding such as AV or selinux.