Hi,
I am currently using some monitor software and tools to check how my system react with different Fullscreen and Windowed mode.
Fullscreen will end up forcing one of my 12 CPU thread near 90%+, windowed mode, all CPU are equal load.
Fullscreen runs well with GSync, windowed mode smooth Gsync but a bit stuttery.
3930k 4.6Ghz 6 core / 12 threads.
GTX TITAN, 1050Mhz core.
32GB 1866Mhz ram.