I have rarely had any bus issues at OKW. Usually we have waited 10 mintues or less I would say, with many just a few mintues really. Once years ago I waited a while leaving EPCOT, but I have never had another experience like that since. Usually it seems we wait only a few minutes. When last there they did have a refillable mug. In fact there were two types. One was less expensive but then required like a $2 charge to refill, while the other was free refills, but was a "seasonal mug", one specially dated and issued for each season (when i was there it waas "Spring Break"), I guess to prevent them from being reused. As far as the pool walk, there is the main pool and then several "quiet pools". I have never had more than a few minute walk to a pool, but I guess some of the units could be in the 5-10 minute range, perhaps even longer if you wanted to go to a a specific pool, like the main pool, as opposed to the one closest to you. I guess the buses could be used to reach internal spots like the pools should you desire. I find it only takes me about 10 minutes to walk to the main pool, but I walk at a decent pace.
Hope this helps.