I don't think you can upgrade rooms. After 12 trips, I've never seen anyone ask or try. Oddly enough once in Saigon when we arrived for an ABD arranged prenight, the hotel asked if we wanted to upgrade, but I'm thinking that was Vietnam and was the exception.
Most of the hotels and rooms are quite good. Your opinion will of course depend on your experience. Some of our rooms have had amazing and definitely not standard views. In Zermatt, we had a balcony that overlooked the Matterhorn. In Guilin, the "Gum Drop" mountains. In Rotenburg, overlooking the main historic front street. In other places, it was obviously not the prime view. At the Peninsula in Shanghai, we had a view of the courtyard rather than the Bund. In Laos, our room was on the lower level without much view rather than overlooking the beautiful jungle. And often it's luck of the draw. I've been on the Africa tour twice. Once had a spectacular view overlooking the Indian ocean in Knysna. The other time (same hotel) we overlooked the opposite and less interesting side of the hotel. I think it was a golf course. And some guests will be assigned better views than others at any given hotel. It's very luck of the draw. You have to be cool with some randomness on ABD. As was mentioned earlier, you're not in the room very much.