Ok, that makes sense.
I still haven't tuned memory timings.
I have 2x8GB Corsair Vengeance RGB 16GB DDR4-3466MHz CL16 (CMR16GX4M2C3466C16)
Memory runs fine @ 3466 spec and higher (but it starts to relax timings).
Anyone knows what memory dies brand are in this?
3700X @4GHz:
DDR4 3600MHz auto (CL26) - 6.8Khs
DDR4 3600MHz tuned (CL16) - 8.4Khs
+23.5% - because of tuned RAM

UPD 28/11/2019: decr. trfc from 345 to 278 gives +150h/s, so it pushes 8550h/s so far