The Su-Hua Highway was one of the highlights of my recent trip to Hualien and Taroko Gorge. We drove our rented car along a stretch of Su-Hua (Highway 9) which is easy to access from Taroko Gorge or the north of Hualien. I highly recommend going during the week when the traffic is lighter.
There are plenty of places to pull to the side and take photos or explore established trails that lead to further look-outs or down to rocky beaches. Also, notably, many of these rest-stops have public bathrooms. There are also places to stop for a snack or for some souvenirs along the way, and plenty of excellent opportunities for landscape photography. I highly recommend this drive if you're looking for a relaxing and scenic way to spend an afternoon.