Hmm not sure about bottom tree arc, I usually don't play arc warlock and when I do it's mostly middle tree. For middle tree, what I do to get back my super back ASAP is use a void CWL mod called Energy Converter that gives you up to 50% of your super back when you use a grenade. So at 5 stacks of CWL, if you're at 0% super energy you get about ~40% back, and less if you're at more than ~10% super energy.

Whether to use Dynamo or Ashes to Assets I don't think matters a ton, but prolly should pick based on which of your abilities you can get back the fastest. I personally lean towards Ashes to Assets since it's 1 mod slot less than Dynamo, pairs with Energy Converter, and can use Bomber and/or Grenade Kickstart mods along with a Demolitionist weapon to spam grenades.