Thank you guys for your responses.
I was very stubborn yesterday and tried to pass through different topics related with the TMC drivers, even some of them explicitly said "it's not your case...". I found accidentally something about _VQUIET, which is not mentioned in the general manual (or I missed it). I thought it's misspelling, but I tried...
My setup works with it! That's fact, the drivers are hot a little bit (~70*C), but they can do their job. The mount performed teens of GoTo jumps and didn't stopped in the way. I still have some problem with parking, but it seems to be another problem, rather related with the KStars-Ekos: the OTA sometimes stops far away from the home position, but deceleration is proper.
I use stepper motor bought in China, its hard to say about their brand. Simple Nema 23 motors, around 1.5Nm (Ra) and 1.2Nm (Dec). That's right, the current is close to end of the range, so this is first disadvantage. The DM556 drivers can work with over 5A with no stress and they have huge heat sinks! Another disadvantage of the TMC5160 is that they aren't silent in the _VQUIET mode, while other modes don't work. The stepper motors under control of the DM556 are almost entirely silent.
Presently I don't use the PWM outputs for the dew heaters, I have made my own system of the heaters and it works well. But it's good idea, one device less. I'll think about it later.
What benefits of using the FYSETC S6 3D board instead of the MKS Gen-L v2.1 is apart the 32-bit unit? Is the slew faster? Can I use GPS and WiFi/BT module straight with the board? I use a USB GPS module, so the Ekos knows where it works. I don't need the WiFi/BT now, but it may change if I find solid reason for it. :)
Thanks again for your advises.
BTW, please give me some time for finishing the mount before you place it in the showcase. I want to paint it and make a box for all the electronics.