Sounds weird. I have a potato PC but still, don’t face major performance issues with the engine. I don’t know much about cards but if you can run all those games I think you should be able to run the editor as well.
Have you updated to latest drivers for your new card?
(silly) Also just for checking, run dxdiag and check the display tab to see whether the system has the card installed properly.
Were you getting solid performance with your project before upgrading your graphics card? There are ways in the editor to make you bump performance but if you are using post-process and advanced materials, it would make development harder as they would get turned off.
While running the editor open task manager → Right click unreal engine → go to details → Right click UE4Editor.exe → Set Priority → High.
also, check task manage stats to see which program is eating up your performance.
In your scene, try running in shader complexity mode to see if it is performance friendly.
Try working with unlit scene. etc, some solutions just from on top my head.