Hey there, not sure if you guys figured out the issue but to fix this issue all you gotta do is to append -nohighdpi to your UE4 launcher and that should solve the issue.
Other way is to change the widget scale float inside the engine and then just recompile the engine. The float is here: Engine/Source/Runtime/ApplicationCore/Private/GenericPlatform/GenericWindow.cpp>FGenericWindow::GetDPIScaleFactor() => just change the return value to whatever you want and recompile the engine.