Waveshaper Tideseer Mantle with Lich Witch

Will the Waveshaper unique explicit modifier "Increases and Reductions to Mana Regeneration Rate also apply to Energy Shield Recharge Rate" apply to the Ascendancy passive modifiers of "Soulless Form"?

Or does the explicit bypass this passive and go strictly off your mana regen rate to add to your energy shield recharge rate?

If it goes off of the "Soulless Form" passive, does that also mean it will go off of the 6% of maximum life regen?

It shouldn't interact at all. Soulless form just replace the inherent Mana Regeneration (4%/s if I remember correctly) by a Life Based instead. It doesn't affect your Increases/Reductions to Mana Regeneration rate.