Olaplex is not a protein treatment. It’s a bond rebuilder. The Olaplex will rebuild some of the broken disulfide bonds, and a protein treatment adds a protective barrier to the strands, and will fortify any compromised areas of the cuticle layer. I’d recommend you do both. You can do them back to back.
Start with Olaplex #3 — wash out—hard protein treatment—rinse— moisturizing deep conditioner.
I would do this weekly, replacing the hard protein with a milder one after the first time, until my hair has regained its strength. Always follow with a moisturizing deep conditioner.