As Infojunky suggest the drive is the sightseeing, you dont need aim at particular «stops» for scenery. Drive leisurely and the scenery will come to you, but you need to lift your eyes from the asphalt.
You have at least 3 options, and all of them are scenic:
On your way from Voss to Aurland be sure to include the old road Stalheimskleiva in your trip https:/…
At Gudvangen you could take a boat trip at the beautiful Nærøyfjorden by ferry or kayak
If you're not going by boat you could see some of the fjord if you're driving to the village of Bakka
You could also visit the goat cheese-village Undredal
At Flåm you have of course Flåm railway. And it's a good place for hiking as well.
At Aurland Stegastein lookout is a must. And if you do have a lot of time (which I guess you don't) hiking to mountain Prest is also very, very nice. Grat view of Aurlandsfjorden.
From Aurland to Lærdal the snow road is the most scenic option (unless you have driving the world's longest tunnel on your bucket list). From Lærdal you will pass by Borgund stave church which is a beauty. Mountain crossing at Filefjell.
Option 2: E16 Bergen-Voss-Aurland-50-Hol-Gol
Part A: The same as option 1
Part B: Driving Aurland valley. The road is more narrow than option 1, and there are a lot (!) of tunnels. In my opinion this road is a little funnier to drive than road 50. The mountain crossing is also nicer. But you will miss the snow road and Borgund.
Hardangerfjord is a little less dramatic than Nærøyfjorden and Aurlandsfjorden, but you will see more of it. The most interesting parts are the Eidfjord area (Kjeåsen mountain farm, Måbødalen canyon, Vøringsfossen waterfall) and the mountain plateau of Hardangervidda.