Space consumptions of HW4 and HHW5 are identical. However, the organ definition file (*. Organ_Hauptwerk_xml) and OrganInstallationPackages need to be only once on your hard disk (or SSD). Only cache files (plus a few configuration files, which do not require too much space on your disk) are created for each alternate configuration.
In order to use your SSD as effective as possible, you could leave your OrganInstallationPackages on a second drive. If this is a normal hard disk, the very first run, when the the cache is built, will be slower, but as soon as the cache is created on your SSD, your system works at full speed.
Best,
Chris