We had a three-bedroom villa at Grande Vista two or three years ago and it had a third bedroom that locked-off as an efficiency unit. As this is my only experience I do not know if that was typically of a Marriott efficiency but I thought that was rather small. There was one queen bed, a bathroom, a kitchenette area - I think that it was limited to a microwave, a small (dorm room type) refrigerator, maybe a coffee maker along with some tableware, a television, maybe a chair, and a sofa bed (probably a double). My youngest daughter and her friend stayed in that bedroom so I'm not entirely sure that I've gotten it all exactly correct but I think that's pretty close. I thought that it would be a good size for two people but would be more like staying a hotel room for any more than that - not at all the lodging experience that I'd expect for a family in a timeshare villa. If I remember correctly the efficiencies have a limit of four people per room.
Dick Taylor