Update:
I've connected Dell through DisplayPort <-> USB-C cable omitting I-TEC and issue is no longer visible
So, in summary:
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DisplayLink & MacOS Mojave 10.14.1 = lag, jamming & smoothness drops
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DisplayLink & Windows 10 = everything OK
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NO DOCK STATION & MacOS Mojave 10.14.1 = everything OK
It's obvious that there is something wrong with station. Moreover, it seems that it's specifically related with macOS drivers.