In general, going from east to west, there will be a steep climb at the beginning and a LONG downhill run into the valley. I'd say the most important skill to have regardless of route is being able to manage your speed on the downhills without burning up your brakes or going airborne.
In my class A I've only ever crossed via 80. No shame in doing that, although it takes you out of the way, gotta go through Reno, and still have to manage a high speed downhill run.
50 has a short steep climb past echo lake on a narrow road with cliffs and all. Usually a lot of traffic too. Wouldn't be eager to tackle that in a class A but I've been in worse.
88 has a longer climb but less steep. Probably less stressful, and really pretty besides. Avoid 89.
As to where you cut over, there are a lot of teeny little roads between 50 and 88 that are gorgeous but it can get pretty tight in some places. I've mostly been back there in my motorcycle, typically with no idea whatsoever where I was, or where I was going.
In an RV? Omo Ranch is OK I guess, it gets really tight in some places, I'd wonder about tree clearance in spots. Mormon Emmigrant Trail is pretty and not particularly technical, might be worth a look.
88-49-Pleasant Valley is the easy-button option. You'll run into a little traffic in Jackson but not too much. Been a couple of years but my recollection is, Pleasant Valley road is easy.
I don't think I've been all the way into Somerset, although I might have. Like I said, I was typically blissfully lost the whole time.
2008 Tiffin Allegro Bus