Premium Rental Car Insurance

I was reading through the perks and I noticed amex provides a flat rate of LDW insurance that many rental companies offer.

While it looks impressive, is there something thats in the terms or based on personal experience that should be a caution for it to be used?

I’m planning to rent a Full Size through Hertz/National and wanted to know if I should opt in for LDW or use the Amex Premium Insurance as primary? (Still getting supplemental liability).

For context - I do not have a personal car/insurance.