I recently migrated from my older Powerbook to a new iMac and after making a fresh install of the Poser8  app on the new mac just put my old PoserPro  runtime in another location (in my User>Documents folder ) and linked to it as a secondary runtime. I've even been adding any new library content to that older Runtime because its already organized just as I like. Poser links to it just fine.

Python scripts however definately do need to be in the primary Runtime folder to work as I found out but I wouldn't just drag the old one over to completely replace the new.
Better to duplicate any scripts that you want to keep from the old and put them in the new python folder with a colour label (I do that to easily identify them if they need removing as I have a bad memory ) and try them out from there.

I would also start with fresh preferences too.

I do realize you are moving from Windows to Mac -not Mac to Mac as I was- but at least if you try just linking to your Windows Runtime first you won't be messing up your nice new Mac Poser installation and if all your old content works ok you've saved yourself a lot of reinstalling   ; )

Hope it goes ok !

" Try and be nice to people, avoid eating fat, read a good book every now and then, get some walking in, and try and live together in peace and harmony with people of all creeds and nations."
-Monty Python