This is my experience of how far we can go with reduced VHDs and/or WinPE VHDs until today:
Mini-10x64-LZX.vhd 2 GB, from previous post boots as filedisk very fine on a 2 GB Ram PC (Free Ram 1.2 GB).
Also capable to Ramboot very fine on a 4 GB PC as I have tested since long time ago.
NOTE: This is a recicled 2 GB VHD, to be exact it was intentionally made of 2046 MB, not 2048 MB to be on the safe side, because of an old issue in grub4dos for UEFI, fortunately yaya solved this issue since some time ago.
EDIT: After recapture and reapply LXZ Compacted, numbers from previous post after first boot, are even a little better, previous number were: used space 1.59 GB and free space 404 MB.
Now used space is only 1.57 GB and free space is 426 MB, free Ram is 1.2 GB, about same free Ram as my normal installed 10x86 (same build) on real internal drive.
Please see Mini-10x64-LZX.png (last photo, just attached).
After recapture and reapply in Wimboot mode the VHD from previous posts this are the data.
800 MB VHD >>> 463 MB used size >>> 333 MB free size >>> 471 MB free Ram >>> Ramboots very fine on a 2 GB Ram PC.
VHD is 800 MB + 1.15 GB linked Wim file = 1978 MB = 1.93 GB Total required space.
If VHD is externally lz4 compressed vhd.lz4 file is 122 MB + 1.15 GB linked Wim file = 1300 MB = 1.27 GB Total required space.
From info mentioned on this post.
500 MB VHD >>> 174 MB used size >>> 324 MB free size >>> 550 MB free Ram >>> Ramboots very fine on a 2 GB Ram PC.
VHD is 500 MB + 765 MB linked Wim file = 1265 MB = 1.235 GB Total required space.
If VHD is externally lz4 compressed vhd.lz4 file is 47 MB + 765 MB linked Wim file = 812 MB = 0.793 GB Total required space.
Please see attached photos.