This comment really highlights the fact you haven’t read 2e and 3e source books. The shit your talking about is embedded in the lore and part of the restrictions 5e/Mystra imposes.
I’m not trying to be elitist but you are ignoring aspects of cosmology, religion, and mysticism that actually do matter in the worlds in question.
Even for Tolkien (a totally separate cosmology) you are being dismissive as you neglect the fact that elves are educated in the bardic magic system of middle earth.
Depends on the system mechanics; 3.5e/1e that first one will have way higher AC due to Natural Armor, Mage Armor, and the inevitable Monk dip.
As to the real world, so long as breastplate doesn’t have a concave catch point at the underboob the second would be both practical and effective. The riveted decorative “cleavage” at the top is actually fairly common and practical for diverting arrow/lance splinters away from the head and neck.