Mackelt

Ryzen 5 2400G $170, a b350 motherboard $60-80, psu $25-40, 8gb memory $80-90, 60gb ssd $30-50, 1tb hdd $50-60. 

First, i5-7400k? I think you mean 7600k or 7400. Second, it depends on your resolution and what games you play. If you turn on a FRAPS monitor, you can check your CPU/GPU utilization in games, and if you aren't hitting your targeted frame rate, and your gpu usage is under 100 or 99% while your CPU usage is around 90-100%, then you might be CPU bottlenecked. 

Pls don't get 1080p monitors larger than 24"  ._. 

Ryzen 7 1700, 16gb corsair dominator 3000mhz, gtx 1080, 2tb Hdd

It seems that you care about longevity of your GPU, so i would save for the gtx 1080 ti because that card is honestly not going to be dominated by another card probably for at least a good while in regards to the performance it can dish out vs the price.

Small increases in fps won't be day and night differences, but small decreases do get quite noticeable when you are playing at competitive refresh rates like 144hz and 240hz. 60hz to 90hz is a big difference for sure but 60 to 75 really isn't much of an upgrade. 

I have the strafe rgb mx silent and I have loved it. Corsair software is dogshit like expected but it still works out in the end

Yes that worked. Thank you!