OKW does now have a separate booking category for rooms that are "close to the Hospitality House." If you won't have a car, I'd suggest making every effort to get booked in that category. That will put you in a building that's less than 5 min away from the pool / gift shop / front desk / restaurant complex.
If you are not in that category, it means that you will be further away. South Point is probably a solid 15 minutes away on foot.
The good news is that the theme park buses can help you get around. Every single INBOUND bus will make its final stop at the Hospitality House. So if you are headed to the pool, Olivia's, etc. you can simply walk to the nearest stop and board the first bus that arrives. Then you disembark when it arrives at the HH.
The trick is getting back to your room. If you don't want to walk, you need to wait for a Downtown Disney bus. The DTD buses will stop at the Hospitality House both as they arrive AND leave the resort. So, when you see a DTD bus, you first need to ask them if the driver if his next stop is elsewhere in the resort or if he is headed to the parks. If he is headed to the other resort stops, you can use that bus to get back to your room.
Whether this presents a challenge for you largely depends upon your intentions. If you will be using the dining plan and intend to get breakfast at Olivia's each day, then you could be set-up for some frustration if you end up in one of the more distant buildings. But if we're just talking about 2 or 3 trips to the main pool or gift shop during the week, I don't think you'll be terribly disappointed in the experience no matter where you end up.
And, no, OKW does not share buses with other resorts.