Lazy-load vs eager render: the viewability/fill tug-of-war

Lazy-load vs eager render: the viewability/fill tug-of-war
Confirmed: aggressive lazy-load fixes viewability scores and quietly drops total impressions — and people only see the RPM, not the volume.
— Eager render (load on page load): max impressions, lower viewability, hurts vCPM deals.
— Lazy-load at fetchMarginPercent: better viewability, fewer wasted impressions, but too tight a margin starves below-fold fill.
— GAM lazy-load and Prebid lazy-load fire on different triggers — running both uncoordinated double-counts and misfires.
Impact: Set fetch margin around 200-500% viewport, measure viewable-RPM not just RPM. (confirmed)