Performance issues with PC. Anyone have workarounds?

I have horrible frame rate issues during game and on title and menu screens. Also lag in-game. I have a decent connection 50mbs, and my rig is still a decent gaming rig. Has anyone have any ideas how to get better performance?

Something to note, i have to run game in windowed mode to work with my frame rate. 1920 x 1080. I can get it to run in lower res without windowed but it doesn't look right.