Question with regards to totem damage vs. spell damage.

Hello I started playing a totem build recently and I was wondering if spell damage and totem damage stacked on the same damage multiplier. Since I have Rain of Splinters I was wondering if it would be better to get shamanistic fury or get the witch spell nodes.

All "% increased x damage" stacks additively. So 10% increased totem damage, 10% increased spell damage, and 10% increased elemental damage would give a +30% multiplier to the damage of any elemental spell totems you have.