Quote - I don't understand this as threads is normally expressed per process

well indeed it's strange for me as well, but I have noticed that, since I marked the "render in a separate process", the two core won't work at full capacity:
number of threads = 2 then FFRender.exe gets up to 56% of CPU time
so I changed and
number of threads = 3 then FFRender.exe gets up to 98% of CPU time

if I disable "render in a separate process", then poser.exe is able to take up to 98% with a number of threads = 2