When gaming at 1440p would this card be handicapped by an overclocked 3570k compared to say an i7 7700k?
At 1440p probably not at 1080p maybe depending on the games.
What you will see with a i7 7700k is much better minimum FPS and slightly higher higher average FPS. This would make for smoother gameplay.
You will still get the GPU at 100% load on most games at 1440p, what overclock do you have on your 3570k? TBF 4.2Ghz and over should be fine anyway.