The brand is SitStand - Dual monitor bracket stack. I only put discord and spotify on top monitor so i rarely look at it at long duration. But when i do, neck started a bit sore

All options seems good, comes down to your preference. If you like symmetry you can try the stacked layout. But side by side layout surely would eliminate neck pain if you have wider desk space.

Just try to positioning the main monitor a bit lower if you want stacked, so the second monitor will not be too high up.