Yes you will struggle to get a Windows 10 VM much below 40GB unfortunately.
The expansion card did work, but install a thermal pad to manage the heat. When the card throttles, Windows runs very very poorly.
The advantage of using an expansion card with Ventoy is that you can install multiple OSes on the card and choose on boot. Those just consist of single .VHD files. You can install and configure them on another machine if you want.
