Train & Ferry or Rental Car: which is more economical?

Norway isn’t particularly accessible by trains. If you want to see natural wonders the choices are mainly car or bus. By water there’s the Hurtigruten ferry that follows the coast, and the various cruise ships.

It’s all expensive but the trains and Hurtigruten will be much more money.

I will have to disagree with Tom a bit. The train from Oslo to Bergen across the Hardanger Vida is spectacular. An off the beaten path trip is to take the Telemark Canal from Skien to Dalen in Telemark. Skien is a couple of hour train ride from Oslo. Spend the night in the 19th Century hotel in Dalen and then take the bus to Bergen.

I guess without knowing if they want to see Geiranger Fjord and other off-train destinations we can't really say what is best.

Thank you all for your help and advice!
Every travel book I've read says that Scandinavia is very expensive which is why I'm doing a comparison between organised tours and traveling independently. I didn't mention that we're from Australia, so due to current travel costs and exchange rates, this part of the world may be unaffordable for us but hoping we can make it happen in 2021.
Will most likely have to reconsider the dates we travel. We prefer to escape our winters but that's Scandinavia's high season.

I think the Scandinavian cost hype is exaggerated. Denmark is not pricey, same as typical Europe. Sweden is more but not significantly. Norway is the most for sure, but if you are willing to rent cabins/apartments where you cook some meals and self-drive it's just not that much more, maybe 10% over the average Europe cost, that is if you are willing to teetotal, avoid hotels for Airbnb-type lodging, and limit meals in restaurants.

Thanks Tom! You're right, there's always ways to budget better in terms of accommodation & meals!
Kind regards to everyone for your help and advice.