SR OS documentation can be fetched from this handy site: https://bit.ly/iondoc Open the 7750 section and choose the needed version.
Documents which require login are marked with "key" icon. The rest can be opened by anyone.
vSIM installation guide provides the details on how to launch virtualized SR OS and its configuration options.
To save on disk space the guide uses libvirt backing store technique, which allows a user to use a common disk image for every guest and each gues will have its own disk image with deltas only.