Which Way in California?

99 & 395 are very different types of roads. Simple explanation goes like this. 99 is a freeway. 395 is part 4 lane divided road, part two lane. 395 is desert. 99 is Central Valley. If you want to see Big Pine & Carson City, 395 is the one. There are far too many great things to see along the route to enumerate. Tons of little streams & lakes along the way. Mammoth & June Lake loop. Convict Lake is pretty spectacular. Leave the towable at a site & do a day trip up Tioga Pass. There are small non-hook-ups campgrounds up there but at that altitude at that time of year weather can get nasty. (Donner Pass isn't that much further north. You know what happened there!) There are definitely ways to cross the Sierra in RV's. I took a Class C up 50 & around Tahoe about 2 decades ago. We recently took our 37' Class A gasser pulling a C-RV over I-80. Even stopped for a snack near Donner Pass. To access Yosemite, Sequoia & King's Canyon you will need to come at them from the western slopes of the Sierra eventually. Though I haven't done it, I like the suggestion of 88 to cross the mountains. There's reputed to be a great RV park near Jackson. Then use 49 along the lower western Sierra to access the parks. Either take your whole rig into the parks (I'd start checking for availability now) or park the towable and day trip it. (Our last trip to Sequoia, we left the motorhome in Visalia & drove the car. Long day, but hugely worth it. I'd highly recommend lunch at the lodge.). You can spend a great deal more than 2 months exploring either of these areas. Watch the weather. Big winds come off the eastern Sierra in the afternoons at times. And snow is certainly possible at the higher elevations. One of our best excursions was into Yosemite Valley during a snow storm just after Christmas. Fortunately had just the 4wd drive vehicle for it!