We are traveling from Norway to Sweden on a high speed train on Sunday July 30th. We would like to know what to expect in terms of regulations and custom inspections upon arriving in Stockholm. Thank you for any information you can provide.
Both are in the Schengen Agreement area, so it should be a non-event.
https://www.schengenvisainfo.com/schengen-visa-countries-list/
Boarders between Nordic countries are pretty much just lines on paper. Highway signs may note borders in a low key way. Blink and you will miss the crossing. A number of years ago we skied across the Finnish-Norwegian border (the Tana River was frozen) and didn't see anything indicative of a national border.
On the other hand, take care not to cross the Finnish-Russian border. Four Brits found out the hard way:
https://www.theguardian.com/world/2017/jun/20/britons-detained-crossing-finland-russia-border-beer
Totally a non-event. You wouldn't even know you were crossing a border if you didn't see a sign saying you are now in another country.