Larian Studios Forums Divinity: Original Sin 2 Divinity - Original Sin 2 - General Thoughts on single player experience

I have a more general question:

Are D:OS1+2 designed as single player game with the option to have a multi player ( like baldurs gate) or as a multi player game with the option to play alone?

I played D:OS1 as single player and it was one of the best games I have ever played.
But some things seemed very strange to me until I realized that it can be played as multi player (2 main characters, RPS between player characters, no pause, . . . ).

I have not played a multi player game for a very long time. The only multi player RPG (not MMOs) I have ever played was Secret of Mana.