@mak: x64dbg is developed on Windows 8.1 x64. There are indeed many plans to improve the performance of these kind of things, but it is really hard to benchmark and even harder to improve. Feel free to improve things and send a pull request.
That error message is from ScyllaHide. In their readme file they explain why it happens and how to fix it.
And until now there were no plans. Feel free to report if you have ideas or made anything
here.