For some perspective, you have the two key arterial routes in/out of Sai Kung, Sai Sha Road and Hiram's Highway, undergoing widening and realignment as we speak and will be for the next few years. Details on Sai Sha Road's works are articulated in GeoTommy's post. The first phase of the Hiram's Highway improvement works (from Clear Water Bay Road to Marina Cove) is expected to be completed in the next year or two (I heard end of 2020); the second phase (Marina Cove to Sai Kung Town) has yet to commence and is in advanced planning stage.
If you don't have to travel in and out of Sai Kung then it is definitely a lovely, quiet place to live in; if you do, bear the above in mind when making your decision. All the best.