I think it depends what you want by chill.
Honestly Riviera for me because its a single building and doesnt get a bunch of foot traffic. That being said I need a resort that is somewhat connected to the parks and preferably Epcot.
Places like BLT/VGF/POLY/BWV/BCV all have too much foot traffic to be chill in my book.
Also OKW is more like a retirement community and SSR is like an apartment complex.