I have an i5-3570. I have previously been told that an upgrade to (for example) an i7-8700K would see a significant improvement and would be well worth the investment. This article seems to say the exact opposite.
I presently have a 1920x1080 monitor and GTX960 GPU. My system is used for general office applications, surfing and limited gaming (WoW, with an intention to switch to Elite: Dangerous shortly).
That I couldn't say - as I'm not familiar with those particular games or how demanding they are.
Might be more appropriate to start a separate thread though, for that question. That way you're more likely to get people who can address that question than who would see it buried in the midst of this thread about the hierarchy charts.
The amazon prices showing for the likes of the Ryzen 2600X are inflated as they're displaying the price for a combo deal with a Corsair AIO. Not very helpful as price is a huge factor and the Ryzen CPUs already come with their own cooler.