The characterization of property as quasi-community property under this chapter shall be effective solely for the purpose of determining the disposition of such property at the time of a death, and such characterization shall not affect the rights of the decedent's creditors. For all other purposes property characterized as quasi-community property under this chapter shall be characterized without regard to the provisions of this chapter. Both spouses or both domestic partners may waive, modify, or relinquish any quasi-community property right granted or created by this chapter by signed written agreement, wherever executed, before or after June 11, 1986, including without limitation, community property agreements, prenuptial and postnuptial agreements, or agreements as to status of property.