Our two night stay in Balestrand was my favorite part of our visit to Norway in 2019. The way we worked it into our itinerary was to travel the complete Norway in a Nutshell journey all the way from Oslo to Voss, leaving on the 6:22 a.m. train from Oslo rather than choosing the second departure time. In Voss we picked up the rental car we'd booked from Hertz and drove up to Balestrand. After two nights there, we drove to Bergen, and returned the car there. If you decide to rent a car, you'd probably want to save the hefty one-way fee by returning the car in Voss and taking the train there back to Oslo. The driving was quite easy. You may find that it is nice to have a car in Balestrand. It's a lovely little town to walk around in, but there are things to do in the area that would make having a car a plus.
The Hertz rental car facility is actually just before Voss as you are on the bus from Gudvangen. Using instructions provided to us by the owner of the Hertz rental car facility, we had the bus driver let us out early, at the Skulestandmo bus stop. (I was worried he wouldn't be willing to stop the bus before reaching Voss, but this request was no problem.) From there we had a five minute walk to get our reserved car.
The Voss Hertz facility was very easy to work with. When I was first looking into this, I was communicating with the owner by email, but then I picked up the phone and called because these arrangements were too vital to not be sure I'd gotten my booking locked in and knew how to get there. The owner spoke excellent English and assured me that our reservation was secure and our car would be waiting for us, even though we'd be arriving after hours. (Our arrival day was on a Saturday when they close early. His instructions to us were to pick up our paperwork and keys at a gas station next door to his place.)
Back then, the email address I was using to communicate with the Hertz facility in Voss was [email protected]. The owner's name was Stefan. He really was so helpful! At first we were going to pay a little extra to have him drop off the car right where the bus lets NIN passengers off in Voss, but then he had the idea of saving us that money by having the bus driver let us off early, so we could walk to Hertz.