The command
sudo deluser --force --remove-all-files myUsername
should be enough as --remove-home will have no effect with --remove-all-files as this removes already everything. Be sure that there are no files relevant to you owned by other users e.g. root
In Linux, if you are sure you have deleted all personal data, you could use the zerofree tool to zero all free blocks on the file system. You should probably use -f 0xFF to erase the free blocks to 0xFF which on the SSD then should trigger the block erase by the firmware.
Probably a similar tool exists for Windows but I do not know anything about that beast.