Over 80% of sunscreen performed below their labelled efficacy (2020)

Best to wear a hat with a brim and a long sleeved shirt.

Is mineral sunscreen a safer bet than regular sunscreen, since it physical blocks the sunrays?

Much worse, if for no other reason than applying it and having it leave behind a white residue on your skin makes people much less likely to reapply once it rubs off.

I always pack my own sunscreen when traveling to islands that ban normal sunscreen. I feel bad if it actually damages the reefs, but reef safe sunscreen is terrible at protecting from the sun.

That's not okay. If reef safe sunscreen isn't sufficient for what you need, then you should find a different way to protect yourself than one that damages reefs.