I can do 1080x1080 on the updated version of the GUI using my 8GB 2070 Super, and still have enough VRAM left over to fiddle around in Blender while the GUI does its work.
It's kinda annoying that they're paywalling such big updates, I hope they plan to update the Itch version soon so people don't have to pay $10 a month for access to a bunch of different services they probably wont use, just to get the bugfixes, content, and optimization of the newer versions of the GUI.