I have a very large world in my game (16km x 16km), and if you can port to 4.14 the load times and fps seem to have increased A LOT.
my game in 4.12 vs 4.14 is night and day for loading times and fps in game (2+ minutes load time vs ~20 seconds) because of EDL i believe.
try opening your project in 4.14, open project settings and under streaming enable “Event Driven Loader Enabled”. (only works in cooked builds)
if your game is already cooked in 4.14 open your cooked folder, game/config and change defaultengine.ini to enable this feature and watch the load times
and weep happy tears.