Nevermind. I found a way to use project64 version 2.1. I just needed two tricks.
First, and unlike what is said on the emulator's help, you DO need to enclose the rompath with quotes. My "project64.cfg" file:
executable D:\Project64\Project64.exe
args "[romfilename]"
rompath D:/Project64/Roms
romext .rom;.z64;.v64
artwork snap D:\Project64\artwork\snap
Also, to make the emulator exit with ESC, I had to manually change the "Project64.sc3", removing this line:
4172,27,0,0,0,6,0,0
Then I could enter the emulator settings to assign the ESC key to application exit.