Flåm to Bergen by train or bus or ferry?

Bus 950 from Gudvangen up to Voss takes a very scenic route, but I don't see a great way to fit it into your itinerary, since you are looping back to Flam. I suppose you could take the Flam-Gudvangen bus on the day you head to Bergen to take that bus and then connect with the Bergen-bound train at Voss.

Never having taken the ferry between Flam and Bergen (only took the Naeroyfjord ferry), I can't compare that scenery to what you'd see by train. The rail scenery on the Bergen end of the line isn't as dramatic as what you will have seen between Oslo and Myrdal.

Just heading from Flam to Bergen via Flamsbana and the mainline train from Myrdal to Bergen (skipping the scenic bus ride) would involve paying for the Flamsbana again. Of course, the repeat view would still be good, and you might be glad to have that opportunity if the weather was poor on your initial trip from Myrdal down to Flam.

Two journeys of the #450 bus from Gudvangen to Voss (not all buses on that route are #950) have come from Flam- at 0540 and 1635. They then continue onto Bergen.
Flam to Gudvangen is mainly through two tunnels- a 5000 metre one and an 11000 metre one.
The #450 originated in Sogndal.
So there are direct Flam to Bergen buses.

I'd try to take the 950 up to Voss, though. I think the 450 takes a less scenic route.

Acraven - that is not correct. There is only one possible road. The #950 is the local unbookable bus, which has 55 possible stops on the route.
That is the route which has multiple relief vehicles for all the tourists on the Norway in a Nutshell route, but also serves the locals on route.
One bus does all stops, all the reliefs go straight through.
The 450 is the bookable long distance service with just 11 stops, but only actually 8 minutes faster on shared departure times.
You can book the 450 bus sooner than the trains normally, up to 6 months ahead, maybe more.
The main difference is that at Gudvangen the 450 does not serve the ferry quay, an 8 minute walk away.

Two very good reasons for me to use the public ferry and the 450 bus, to avoid as much as possible the hordes of tourists.

From Gudvangen to Bergen the through bus is also usually cheaper than the bus/train combo for much the same scenery after Voss.
At Voss I'm happy to wait, if on the train, for the next one after the Nutshell folk catch.

OK. I guess the route change for the 950 bus 2 or 3 years ago, after some road damage, has made the routes identical. However, multiple sources I consulted in 2022 said the 450 bus doesn't go all the way down to the ferry dock, so there's an uphill walk if you don't take the 950.

I was scratching my head earlier because there didn't look to be as many buses as I remembered running from Flam or Gudvangen, and indeed there aren't on the Vy website.

After a bit of checking there are also the Norway Bus Ekspress routes #420 from Sogndal to Flam, Gudvangen, Voss, Bergen and Bergen Airport, and the #162 from Lillehammer (on the Oslo to Trondheim rail line) to Flam, Gudvangen, Voss and Bergen.
At Gudvangen the 420 calls at the E16 junction (not the ferry quay) so neatly avoiding the hordes of tourists- which it is not designed to handle. Those are long distance services, primarily meant for local and regional needs, so the touristy websites don't mention them. But the 162 calls at the quay

The 420 leaves Flam for Bergen at 0830 and 1510, the 162 at 1408.

There also turns out to be a Skyss Bus 850 from Flam to Gudvangen at 0648, returning at 1648.

Thank you, isn31c and acraven, for your research! I'll look into those options. I'll need to decide, if I do the bus, whether returning on the ferry to Flåm makes much sense - though I do like the option of seeing the magnificent Naeørfjord twice!

Just following up: I'm liking the original idea to return by ferry to Flåm and take a bus from there. It looks like there are two options: a VY bus 450 (16:35-19:25) and also an NW bus 420 (16:10-19:00) - both from Flåm to Bergen (each stopping at the Gundvagen E16 stop, possibly avoiding tourists). Any thoughts on choosing one company over the other? I've not been able to purchase tickets online (may be too early, or may be the issue with North American credit cards - any thoughts?). Thanks!

I don't believe it makes any difference which bus you take in terms of quality of ride.

On the Bus Ekspress 420- if he is anything like right time you'll be going through Gudvangen before the NiN tour boat is due in, so are unlikely to encounter any tourists, whereas if the Vy bus was a bit late there could be some stray tourists come up from the quay to catch it, and if not you may get caught in the convoy of route 950 buses to Voss.

So I think I would opt for the first bus. It still gives 40 minutes transfer time off the Lustrabaatane ferry from Gudvangen.

At least with Vy you will need to pay with Pay Pal, rather than card. No idea about Bus Ekspress.