For a MoG-style game, I think multiple parallel quests would work better. I am not sure why would that be more "arcade" (I think it's the opposite, right?). If you think of the classic RPGs, like Might and Magic, Bard's Tale, etc. there were always many parallel quests you did in whichever order you preferred (although your strength level kind of guided you more or less). Also, if there's different possible orders, then there is more to talk about with friends: "which quest did you do first? I think doing X is better, as I can get that item to help me with Y", etc. 
But as people said above, I think both could work well! So, I just have a slight preference towards "parallel quests"
For a MoG-style game, I think multiple parallel quests would work better.
yeah, I agree. And more replies here agree too, so let's do multiple parallel quests.
Excellent news! Very excited that this is happening!!! 