Ok, problem solved, now my 8700k performs on par with cpu.userbenchmark results. The reason was, for some reason, the motherboard bios (asus z370-f gaming) had CPU C-states as disabled, which didn't let the CPU boost to more then 4.3Ghz.
After enabling, CPU boosts to 4.6Ghz (though I never got advertised 4.7Ghz) it puts it's benchmark results on par with other non-overclocked results.
Regarding CPU-Z results, it looks like those are outdated, before Spectre / Meltdown patches, as on forums and reviews 550 is not an average for non-OC single clock CPU, it's closer to 500.