It's rather interesting that magical arrows in 5e become non-magical after they hit. In other editions you had a 50% chance of the arrow still being useful. With that in mind, I think the bonuses should stack. After all, stacking is the norm in 5e.
After reading this thread and the DMG, I'm not convinced that a magical bow with a non-magical arrow will allow you to hit a creature who is immune to non-magical weapons. As a 2e gamer, I'm fine playing it that way too.
After reading this thread and the DMG, I'm not convinced that a magical bow with a non-magical arrow will allow you to hit a creature who is immune to non-magical weapons. As a 2e gamer, I'm fine playing it that way too.