RE: Which biplane?
Years ago when I first got into RC I built a Andrews Aeromaster from a kit. It was just plain fun to fly and it flew great. I now have sitting in a box a Giant Aeromaster from GP in the ARC configuration. This is my next project after I finish my Balsa USA Giant Stearman. I also think you may like the Waco YMF series of planes.I also have a 33% YMF5 that is just the most beautiful bipe ever to fly IMO.
You have so many choises to think about........I know........ build them all!!!!