All these games have one thing in common, a CPU intensive game engine. I've seen many complaints on here and other forums regarding games with engines coded in C#, C++ type programming which is far more CPU than GPU. Unity is the one behind 2 of your titles, 2 are Unreal 4 powered games (slightly more even usage).
One point is the PSU sort of. I do think you should run a 700-750W Gold with 2 PCIe power cables instead of one with the dongle built in. If you can add another or the current PSU has another 8 pin, use it and see what happens.
You can also try going into the Radeon tuning area and slide the minimum clock to within 100Mhz of the maximum clock, while using the undervolt setting of about 1.000mv and increasing the power limit to the max. Turn off the zero RPM fan option as well, stock fan curve should be ok but you might want it a bit more aggressive.
It is a PCIe 4.0 card on an older Z series chipset that runs at 3.0 and board power delivery might not be optimal not to mention the memory bandwidth you're missing. In theory the card should work with your setup and it might just be a game engine issue, PSU possibly. That's why moving the clocks closer will help avoid spikes in voltage/amps from the card. Nvidia has a similar spike issue with the 3000 series cards, so they're no better.
Here's my settings, similar card but can't say that exactly copying my settings will work but might. You're VRAM might only be able to do 2100.
