Hello, i am curious about traveling from Oslo through copenhagen to Stockholm using regional trains. Is it reasonable to buy local trains at the station instead of pre booked trains? I like not being on a set schedule and leaving and arriving when i want.
The answer is similar to your other question. When using the DB schedule search , if you only find fast, reserved trains shown on your first search, then try adjusting your request with "Means of Transport = All without ICE" to see the slower regional train options. There are not many departures directly from Oslo to Stockholm, but there is more service between each of those cities and Copenhagen.
Trains are drastically expensive and not always convenient. I'd guess most locals take planes to get between cities because they're faster and cheaper.
If it was my vacation, I'd fly into Hamburg and rent a car or, alternatively, make the trip using ferries (which are also really expensive) to experience Scandinavia from the sea.
Train are not drastically expensive if you buy in advance. For example. a non-refundable ticket on a fast train from Copenhagen to stockholm bought 3 months out can be as little as 195 SEK. That is about $26. You can save a lot of money if you can commit in advance. Plenty of locals use the train, although sometimes flights are less expensive but you have to factor in the cost of getting to and from the airport. Prices for the train will be more expensive on the day of travel unless you are under 26 and can find a "sista minuten" (last minute) special. Use the SJ site (sj.se) to check prices and schedules rather than he DB site as the Swedish site is quite easy to use.
There used to be an overnight ferry between Oslo and Copenhagen. You might see if that is still running as it can save the cost of a hotel room.