No, you do not give up control when you set the Legacy platform to be revocable. You keep as much control as you want. As the creator of the account, you retain the power to change beneficiaries, and add or withdraw cash at anytime up to delivery of gifts.
Yes, you do give up control when you set your account to be irrevocable. From then onward your decisions become irreversible. However, you then gain protections against creditors and taxes.
We recommend you speak to a financial advisor, to determine what is best for your particular situation.