As I understand it, if your ads show as "Eligible", they will show on Google SERP, but will not show on the Display Network. If I only want the ads to run on Google SERP and select in Campaign Settings to do just that, will my ads ever reach "Approved" status? Doesn't matter, I guess, but I am curious to know if they will even review them. By the same token, does this mean that EVERY ad will eventually be reviewed by human eyes?
They will get reviewed and make it to Approved status eventually. And yes, it's reasonable to assume that every ad eventually gets reviewed in some manner, though I imagine if it's not flagged by a bot any manual review will just be random or cursory, because there's no way they'd have time to review every single ad in depth.