I've ridden most of 395 and driven all of it. As I recall, there is typically a very generous shoulder for the entire route, but it usually comes with a rumble strip, also. Traffic is light to moderate, especially north of Mono Lake, but gets heavier as you approach Carson City. There is a significant climb just north of Mono Lake (which I forgot the name of), but otherwise it is fairly flat.
Highway 89 is much smaller than 395 and does not have a shoulder. Traffic is lighter, however. If you take 89, you will have to climb over Monitor Pass to get to Markleeville. There is essentially no climbing on 395 between 89 and the Western Express. I think 89 is a much more scenic and interesting route than taking 395 into the Carson Valley.
Highway 88 over Carson Pass is wide open, with a large shoulder and moderate to heavy traffic. The view from the top looking down on Silver Lake in one direction and out to the ocean in the other is nice. If you are unlucky and catch a headwind, the climb can be a bit of a grind. The decent is much nicer, through the forest and all the way down to Ione or so.
If you are feeling adventurous, consider taking 108 over Sonora Pass and down into Sonora, and then following 49 north through the Gold Country back to the Western Express. It will be a much more challenging ride on smaller roads, however.
One other option is to take 120 over Tioga Pass, through Yosemite, and then following 49 north, but I don't know anything more about the route.
Sean