is nac the same as glutathione vs Glutathione: Differences & Benefits Meno Clinic NAC (N-Acetyl L-Cysteine):

The copper content of GHK-Cu formulations has been a theoretical safety consideration, given that excessive copper can be toxic - however, the amounts used in cosmetic and research applications are extremely small, the copper is tightly chelated by the peptide (reducing free copper availability), and topical absorption of copper from these products appears minimal and well below levels that would cause systemic copper accumulation or toxicity

Animal vs

Liposomal glutathione is generally considered better absorbed than standard oral glutathione, because its lipid coating helps protect it from being broken down during digestion

Cellular regeneration

NAC (N-acetyl cysteine) is a stable form of the amino acid cysteine that your body converts to glutathione inside cells