I’m heading to Yuanyang next week on Wednesday. Will the rice terraces be flooded by then?

Some of the terrace will have been flooded by then, so you can take some good pictures. Let's pray for good weather.

For accommodation, you can stay in the Duoyishu Village and the Duoyishu International Youth Hostel is suggested. The roads are zigzag to the terrace, so you can rent a local car or charter one with other travelers. I believe there will be tourists going there as well at the mentioned hostel. So you can also ask your hostel for help.