To the OP, unlike many I don't see 199 as a great route to Coos Bay, we prefer 138 to 38 from Sutherlin. There is a fair grade just before the junction with 38 but easy to climb. It is scenic but scenic is different for everyone. It is mostly small towns and farmlands with 38 following the Umpqua River. Coos Bay is just thirty minutes down the road from Reedsport.
Winchester Bay RV Resort is not a high end resort. Their prices are reasonable and the Bay is beautiful. Sea Perch is HIGH END and they are SNOBBISH and they are PROUD OF IT.
Having lived on the Oregon Coast, visited family and owned a home there, I think I can speak from experience about a few things you will experience but, I will stick with, as stated 101 is best seen North to South, there are a lot of places to camp but very busy in summer and the only real fast, direct and wide highway in Oregon is I-5 and the highways in and around Portland, and that is a good thing.
Much of the asphalt from I-5 to anywhere else but especially the coast is much the same as it was in 1949 when I first went to Florence to live with some friends and my older brother for summers. Those roads are to be enjoyed and savored, not sped through and ignored, they all have difficult spots but as a wise man once said, "Getting there is not half the fun, it is all the fun". He was talking about making a business successful not road trips but it is good advice to truly get into the drive.