If there's no direct method, DeSmuME is an open source emulator, that means you can create a custom build with the option to make the window borderless. While I've modified the DeSmuME source code before, I'm a bit unfamiliar with the Windows API...
I may try the new ram site, and download more RAM to my Switch. Not sure if ddr3 is the right ram
for it tho. Edit- no it uses floppy Ram, just like @AncientBoi