I've heard the zinc kind is less likely to leach bad chemicals into your blood stream. is this true?

I don't know if its been conclusively proven yet, but the more natural zinc sunscreens (not all zinc sunscreens are that natural, some of it is marketing) have mostly zinc (and a bit of some other stuff of course), while some of the chemical ones have an impressively long list of random chemicals. On that basis I personally believe a zinc sunscreen is less likely to have future unknown side effects.

Avoid nano zinc and yes, it sits on the surface. The chemical ones absorb into your skin.

It's all very safe; certainly safer than sunburns.