If I have a second class Scandinavian rail pass and I an traveling in June from Stockholm to Myrdal and then from Myrdal to Oslo about how much more pas a pay for reservations for two travelers? How about travel from Helsinki to Pannainen and from Umea to Stockholm and Oslo to Gothenburg or Copenhagen, do these trips require a reservation?
Most of your trains through Sweden and Norway will require a seat reservation of $5-20. The DB link at How to Look Up Train Schedules and Routes Online is the best indicator of that, when details for any route say "Subject to compulsory reservation." From Oslo to Myrdal, it only says "Please reserve," but that's highly recommended for June travel. Some of these reservations will only be available once your arrive in the region, but the first couple of legs are currently bookable for spring dates at https://ricksteves.raileurope.com/us/rail/point_to_point/triprequest.htm. If you're not buying the Scandinavia pass for a couple of months, you may be able to book it all in one shopping cart.
Copy and past Pännäinen into a schedule search if that's easier than typing the accents. The daytime trains don't need reservations.
If reducing transportation cost is a goal, check on single trip ticketing as an alternative to a rail pass. The Finnish and Norwegian rail systems have various discounted single trip passes.
Finnish system includes a number of discount groups:
The Saver ticket is always the most affordable choice. Only a limited
number of Saver tickets are available and no discounts are offered for
them. The Saver ticket is the perfect choice, letting you choose your
travel dates flexibly. Saver tickets are offered 60 days before your
departure. You can change your ticket for 5 € and pay a 10 €
Cancellation insurance. https://www.vr.fi/cs/vr/en/saver-ticket
In addition to advance purchase discounts, age has its privilege:
On long-distance trains, passengers over 65 years of age and
pensioners under 65 years of age receive a 20% discount off the normal
Basic ticket price.
The Norwegian system also has discounted fares.
I have taken advantage of the advanced purchase Minipris fares.
The offer is available for a limited number of seats on NSB Regiontog
(inter-city) departures. Minipris tickets can be purchased online here
at nsb.no, using our app, or from our ticket machines. Minipris is an
offer determined by the interaction of demand and availability.
Consequently, price may vary over time and you may find fewer Minipris
tickets on the most popular departures.
Sweden also has a huge range of ticket prices, hard to even describe, for sale at www.sj.se. Whether or not all of these sites work well with US credit cards is something you'd have to test; issues have varied in the past. A Scandinavia pass is one of the cheaper ones, e.g. $265 per person for 5 travel days within a month in 4 countries.