OK,I would echo DWU's advice about the GPUs,as a Polaris refresh has been rumoured but if the RTX2070 is nearly £600,I suspect the GTX2060 will be out of your price range,or there will be multiple models,ie,a GTX2060SE,GTX2060,GTX2060TI,etc unless Nvidia surprise us and have a big gap between the RTX2070 and GTX2060. Of the current GPUs,the RX580 will be the better choice
IMHO,as the extra VRAM will be useful at qHD,as even my GTX1080 can get pushed with regards to VRAM usage.
In terms of the CPU,for open world RPGs and RTS games,I would say Intel has the edge due to the nature of the engines used,but I have a few issues with going Intel currently:
1.)Prices have jumped up to silly levels due to 14NM shortages
2.)If you going for the mainstream 6C/6T CPUs,how will these fare in a few years time,when the new consoles are released and Intel has even moar cores?? I suppose that is a hard one to say.
3.)At least with my old IB CPU,the security patches didn't help my modded FO4 game as it is I/O dependent
The main disadvantage with AMD AM4 CPUs is that they do like faster RAM,and are a bit more finicky in that regard,but the performance jump over your FX8350 is massive though. Also unless you really intend to game at 1080p with £500+ graphics cards,I am uncertain how much of a difference it will make,unless the engine is severely single core limited(like what happens with Fallout 4 if you build settlements). But then again I am using a GTX1080 at qHD,with massive settlements and graphical mods,so that is combination of much more draw calls and more NPCs,so probably an edge case in reality.
If that is too much of a wall of text,the TLDR version is AMD is still better bang for buck currently.