We stayed in Honey Bear last year. Not sure if they are done with construction on US321 now or not, but if steep winding roads give you the willies (they give my wife the same), you definitely want to use the US421 route (it is straighter and 4 lanes all the way into the area).
Watch the switchback curve on the road (Poplar Grove Rd S) heading back to the campground. We had to swing our dually and 40' fiver all the way over into the opposing lane to make it and found a truck and trailer coming from the other direction (it's a somewhat blind curve). Fortunately, they were ready and stopped so we could finish swinging around it.