^I DIY-ed NiN last September 2018.

Easier than I thought. Almost everyone that was travelling in my chosen route had the package, so hindi ako praning kung saan bababa. Everyone was getting off at the same stop/station anyway.
I did the Bergen to Oslo route. I stayed 3 nights in Bergen (AirBnb), 3 nights in Flam (Flam Hostel) and 4 nights in Oslo (AirBnb).
I flew into Bergen from London via Norweigian Air.
Train from Bergen (08:43H) to Voss (09:56) - NOK 210. I purchased the train ticket on the station on the day itself . Wala naman kasing discount if I purchase early, plenty of seats too when I rode the train.
Bus from Voss (10:10) to Gudvangen (11:20) - NOK 57. I bought the ticket via the app. You can also buy the ticket from the driver but there's a NOK 20 surcharge per zone. Since Voss and Gudvangen are in 2 different zones, the surcharge is NOK 40. Nakinig ako sa AirBnb host ko to buy tix via the Skyss app. (I had an EU sim so no hassle for me).
Boat from Gudvangen (11:30) to Flam (13:30) - NOK 475 Fjord Cruise N?r?yfjord - purchased online a day before the trip.
I stayed in Flam for 3 nights. I did one day exploring Aurland (Stegastein viewpoint plus that fjord viewing spot that I cannot recall), and in another day, I took the train from Flam to Myrdal (NOK 390) and walked going back to Flam (20km, 5.5 hours na downhill naman). The Flam to Myrdal walk was the highlight of my Norway leg. Note: I had to repeat the Flam to Myrdal train because I decided to hike from Myrdal to Flam. If you don't want to do this, you can just do the Flam to Oslo train with a stop in Myrdal).
Flam Railway from Flam to Oslo - NOK 639 via NSB website. I purchased this 7 weeks ahead.
The DIY was easier than I thought. Uupuan mo lang nga dapat yung pre-booking.
The downside was the weather when I was in Bergen. It was raining during the 3 nights I was there, so I wasn't able to do the "Vidden" trail that I planned. And Mount Floyen was closed due to strong winds. Weather was better when I got to Oslo.
In my experience, having a contactless credit card is better than cash. There are some food stalls and some museums in Norway, Sweden and Denmark that doesn't accept cash at all. E.g. ABBA Museum in Sweden, and almost yung mga food plazas wherein I ate, they don't accept cash talaga. I still have spare NOK 200 if you want.

After my Norway experience, hindi na ako nag-withdraw ng cash during my stay in Sweden (6 nights) and Denmark (3 nights).