As far as I know, this is expected behavior when booting in live-mode.
It may freeze because you didn’t launch the VM in live-mode. Try booting them in live-mode too.
See also:
and
https://phabricator.whonix.org/T914
This is normal. It can be modified with overlay-size kernel boot parameter in GRUB.
See:
man live-boot
overlay-size=SIZE
The size of the tmpfs mount (used for the upperdir union root mount) in bytes, and rounded up to entire pages. This option accepts a suffix % to limit the instance to that percentage of your physical RAM or a suffix k, m or g for Ki, Mi, Gi (binary kilo (kibi), binary mega (mebi) and binary giga (gibi)). By default, 50% of available RAM will be used.