Thirdly, I presume the increase to 4 workers was to see what you 4070 could do if given the chance.
Already restarting “from scratch” I used the given image to determine if and to what extent the export workers had an impact. Checked the values from 1 to 6 and from 4 onwards the export time no longer improved significantly.
For comparison with 2 export workers, when the NVidia studio drivers 581.57 and 591.44 showed practically no time difference.
ADDENDUM
My PC is an older machine whose lifespan I extended with a new GPU (+ PSU)
→ see here and here.
That is, I’m not expecting performance like that of current computers,
but a (comparable) export shouldn’t be any slower than with PL 8.