If you have ever taken Tioga Pass over to 395, then 88 is about the same type of road as far as the curves go, but the grades on 88 are not as bad as Tioga. I have driven over every Sierra Mountain pass in all types of vehicles. I even took a Class C rental motorhome over Sonora Pass. I'll never do that again, but I made it. Ebbets Pass (4) and Sonora Pass (108) are the only ones I tell people don't do in a motorhome. But 108 has been improved since I did it, and I have seen stories on here of people taking Class A's over it. I wouldn't do it because the road is too narrow in the curves. You can make it, but the potential for conflict with other traffic is high.
Obviously the easiest pass is I-80 just as far as the road is concerned. It's also the most crowded and the trucks take it. Second easiest is probably 50, but only because it's four-lanes much of the way up. 88 is two lanes all the way but it's the third easiest pass. 120 is also two lanes all the way and it's the fourth easiest. Then 108 in sixth place and 4 in last place.