At OKW, the studios will have two queen beds. There will be a portable crib (Pac 'n Play) for the infant.
All of the other
DVC resort studios have one queen bed and a sleep sofa for bedding. There will also be the same portable crib available for the infant.
I agree with bicker - the studios will be crowded for 4 adults. Of course if you are used to staying together in one hotel room, it may not be a problem for you.
The 1 bedroom units have a king bed in the bedroom and a sleep sofa in the living room. There is also a portable crib. The large bathroom is split into two rooms - one had a jacuzzi tub and a sink/vanity and the other has a large shower, toilet and small sink. You will also have a fully equipped kitchen (incl a full size refrigerator) and a washer/dryer. If you are staying any length of time, that washer & dryer is really nice, especially with a baby.
You can rent points to stay at most of the non-DVC resorts, but it will be more expensive than booking directly through CRO/WDWTC.
Best wishes -