The basic ideas of TtR never change (though Rails and Sails gets a little weird with it).
I don't own Nordic Countries. From what I can find on the Internet:
Player count is 2-3 with 40 trains per player (although 45 are usually included).
Tunnels and ferries (from Europe) are included. (You can use any 3 cards in place of a locomotive for ferries.)
The restriction on taking a revealed locomotive is gone, but locomotives can only be used for ferries, tunnels,
or the one 9-length route.
The 9-length route is claimed with X cards of a single color and (9-X)x4 other cards.
The end-game bonus is for most tickets completed.
(Also, the Tallinn-Tampere ticket should be 4 points, not 3.)