We're going to be in Norway in August and we have massive luck that there will be no cruise ships during the days when we're in both Flam and Geiranger - YIPPEE!!! There are small +/- 1000 passenger ships in Molde and Olden at the time. I'd love to NOT reserve or buy in advance things like cruises on the fjords and the Flamsbana so that I have more choice with the weather. Has anyone been in this sort of situation and were things still selling out?
The presence or otherwise of cruise ships at both Flam and Geiranger has little effect on availability of the fjord cruises. The cruise ships have sailed down those very fjords to reach the two villages. Most of the fjord cruise demand comes from the Norway in a Nutshell people and independent non cruise travellers.
So August is peak season, I very much think you need to book.
Instead the cruise passengers take the Flamsbana or go off on bus trips.
If cruise ships do offer waterborne trips they exclusively charter other vessels. When I have cruised into Flam then I have done things independently which are not mentioned on this forum, and are not available to the Norway in a Nutshell people because they are in too much of a rush.
The Flamsbana is certainly likely to be less busy, especially on morning departures from Flam (before the Bergen to Oslo nutshellers arrive).
At Geiranger the ships are met by fleets of buses generally, to mainly land based trips. Mount Dalsnibba is one of the cruise ship destinations.
Please be careful what you wish for. The unfortunate fact is that without the cruise ships the loss making Flamsbana could have been closed in the 1990's and Norway in a Nutshell as we know it might not exist. The line was originally built after decades of trying purely for local use to open up an area previously only really accessible by sea, and only completed after many delays by the German army of occupation.
I understand your joy that there are no cruise ships in port. When we were in Ålesund in 2023 there were no large ships in port. I did prebook a day tour to Trollstigen and, instead of the usual large bus, we were driven in a comfortable van with a total of 5 people. Not all tours will operate when there are no ships in town.
As previous poster stated, you should still consider pre booking any fjord cruise. There are limited sailings with limited capacity.
I've read on this forum about the possibility of sold-out trains between Oslo and Myrdal. It also would not be safe to wait to book that part of the Nutshell route until shortly before you plan to travel in the summer.