If you're flying to Norway from North America, are you confident you'll have recovered sufficiently from the overnight flight to fully enjoy the activities you're planning for July 21? Almost everything in Norway is expensive.
Are you prepared to rent a car for part of the trip? That will affect the advice you receive. I didn't do that, but I know it opens up a lot of sightseeing options that cannot be accomplished efficiently via public transportation.
I didn't get as far north as the Lofoten Islands, and I traveled by ferry, train and bus rather than by air.
Some version of the Norway-in-a-Nutshell route is a very efficient way to see some beautiful fjord scenery while linking Bergen to Oslo. Whether any or all parts of that route are semi-essential for a traveler depends on what else the itinerary covers, but the scenery is spectacular. These are the components:
- Regular train from Bergen to Voss (the least scenic part of the trip). Ticket from vy.no; you might have to use PayPal.
- Bus from Voss to Gudvangen. Pay on the bus; a credit card should work.
- Naeroyfjord ferry from Gudvangen to Flam. Ticket from NorwaysBest.com.
- Flamsbana train from Flam to Myrdal. Buy through-ticket Flam to Oslo from vy.no.
- Regular train from Myrdal to Oslo.
Flam is a very ordinary little town in a stunning setting sometimes considerably spoiled by the presence of monster cruise ships. It is the most convenient place to stay if you want to split the Nutshell route over two or more days. Therefore, demand for lodging is extremely high. Best to pin down that part of the itinerary ASAP and book a room. Make sure it's cancellable in case your plans change. Rooms in Voss, Gudvangen and Aurland don't seem to sell out as early.
Some transportation components of the Nutshell route sell out in advance, but I don't know how early. It's definitely not something you need to worry about now.