Poor graphics performance in Windows when using scaled display mode in Mac

I'm running Parallels 15 on my Mac Mini 2018, 3,2 GHz 6-Core Intel Core i7, 64 GB 2667 MHz DDR4, Mac OS Catalina 10.15.4 Beta (19E258a).
I have the LG 34wk95u ultra wide monitor with the resolution 5120x2160, the monitor is connected through Thunderbolt 3 over UCB-C cable.

I'm running with a scaled resolution 360x1417px on Mac OS and experiencing major performance problems and slow graphics in Windows. I began to experiment with the settings to try to find the problem and concludes that it is related to running Mac OS with a scaled resolution.
I have verified that Mac OS sends native resolution of 5120x2160 to the screen and have selected the option "Best for external display" in Parallels graphic options, I'm using the native resolution 5120x2160 in Windows and scale it to 150%.

On my Mac, if I select the resolution "Default for display" (2560x1080) and I get good performance in Windows, if I select the native resolution 5120x2160, I also get good performance in Windows but as soon as I start to scale the resolution beyond the 2560x1080 I get worse and worse performance.

I also get bad performance if using the option "Scaled" in Parallels and the Windows graphics is far from crisp.

I'm also running the same configuration on my MacBook Pro 2018 and recognise some similar symptoms but not at all to the same extent, does this simply mean that the graphics card on the Mac Mini is too bad?

//Kalle