(a) The right of election of a surviving spouse may be waived before or after marriage by a written contract, agreement, or waiver signed by the party waiving the right of election.

(b) Unless the waiver provides to the contrary, a waiver of “all rights”, or equivalent language, in the property or estate of a present or prospective spouse or a complete property settlement entered into after or in anticipation of separation or divorce is a waiver of all rights of family allowance and elective share by each spouse in the property of the other and the right to letters under § 5-104 of this article, and is an irrevocable renunciation by each spouse of all benefits that would otherwise pass to the spouse from the other by intestate succession, by elective share, or by virtue of a will or revocable trust of the present or prospective spouse executed before the waiver or property settlement.