Mostly solo with some MP. Larian games aren't great for MP if you care about the story/dialogue. They're not particularly bad for their genre: just any incredibly long game filled with tons of one-on-one dialogue and things to do individually (crafting, inventory management, etc) while the other person waits isn't great.
I'll likely only play multiplayer if:
a.) it's still my first-third playthrough and I thus won't get too bored talking/listening to every NPC
b.) I'm playing with friends who have also done multiple playthroughs and thus we can all ignore the story/NPCs/etc for the most part
