Another thing not mentioned is the motherboard you're getting. Even being just a 1700X it will get you into the AM4 ecosystem with a potential to upgrade all the way to a 5600X on the same motherboard in the future. But that depends on the motherboard...so to that end I'd try to get one of the decent B450's. A B450 tomahawk Max would be ideal for this, but there are any number of good ones.
And BTW, I play Ghost Recon: Breakpoint at 1080p on a 144hz freesync monitor at very high settings with a 1700X and it's perfectly fine. I feel confident it would do 1440p just as well but an RX480 just isn't enough GPU.