alt Hacker News> most emulated games will need at least 16 Gigs of RAM at minimum
That's because the RAM is shared with the GPU and most of these games would require a GPU with at least 2-4GB on top of the normal system requirement to have at least 8GB. So, 8GB of RAM would be cutting it close on a mac since part of that would have to be sacrificed for the GPU.
Alyssa lays out the reasoning in the linked blog post.
They are running emulated games in their own separate virtual machine, because Intel games expect a 4k page size and the OS is running with a 16k page size.
Virtual Machines require their own chunk if memory overhead, so the resource usage can't help being higher than a native MacOS game's would be.