Eurorail Pass

Well, at least for Germany, seat reservations are not required, but sometimes nice to have. Easy to buy at 4.50 EUR each for 2nd class. By "rail company" I assume you mean Rail Europe. They're not really a rail company, they're a travel agent.

It depends. Most tickets are steeply discounted if you buy for specific trains at specific times starting about 3 months out. It depends how many trains you are taking. You need to sit down and plan and do some math to determine if a pass is best. Www.Seat61.com is a good place to learn about trains.

Trainline.eu may be the simplest place for you to check the fares you would pay without a railpass. NOTE: Unfortunately, per Chris, you can't get most of your ticket prices from trainline. I guess you'll need to check each rail company's website. If they are not found by Googling, you can enter each international route on Rome2Rio.com and l drill down to find the website link. Do not trust Rome2Rio's fares, frequencies or travel times.

If your travel dates are solidly locked down, use your actual dates to find the advance-purchase fares for non-refundable/non-changesble tickets. If you want flexibility and anticipate buying your tickets just a day or so ahead of time, check fares for today (which in many cases will be much higher).

Remember that any mandatory seat-reservation fees will already be included in the ticket prices you see on the rail-company websites.

Molde, before you buy any pass, you need to read this: https://www.seat61.com/Railpass-and-Eurail-pass-guide.htm

Eurail IS NOT a rail company. It is a travel agent in North America which sells passes, which are valid on the trains run by most (but not all) rail companies in whichever countries the pass is valid.
Even when you have a pass, many rail companies will not yet you on their long distance trains without paying an additional surcharge, called a "reservation fee". If you just buy tickets direct from the rail company, it is often cheaper, especially if you buy earlier and get advance purchase discounts. And these "normal" tickets (what people who live there buy) include everything in the price.

https://www.trainline.eu/ is a European reseller which sells tickets at the same price as the railway companies. But it only covers some countries. Of the countries you list it only covers Germany.

Oops. Thanks for the correction, Chris. I just assumed... I'm a last-minute person, so I buy my tickets after I get to Europe.

Seat reservations are required for the faster trains in Sweden and Finland and are quite strongly recommended for longer rides in Norway. They're not required in Denmark and Germany, except on summertime departures of the direct Copenhagen-Hamburg trains. See our info pages for each country, such as https://www.ricksteves.com/travel-tips/transportation/trains/sweden-rail-passes.

A one-month consecutive Eurail Global Pass may be a good choice for $787 per person in 2nd class (if you have 2 adults traveling together, or less if you're both under 28), but we don't know how many and how long your train trips are. Global is the only version that covers 5 countries. But you can also compare a separate Eurail Scandinavia Pass (maxes out at 8 travel days within a month for $332 per person) and a German Rail Pass for somewhere between 3 and 15 days of travel, either consecutively or within a month. Or maybe you only have one train ride in Germany - we don't know.

If your only travel in Finland is taking the discounted ferry to/from Stockholm (a common plan), then you need not include Finland on a pass. A 4-country Select Pass could cover Germany, Denmark, Sweden and Norway, e.g., $402 per person for 8 travel days or $454 for 10 days within 2 months.

There may also be flights that would be a good value for a long leg somewhere in the trip, like from Helsinki to Bergen; see www.skyscanner.com.