Final upload this time with a render in SF with 3 lights and dynamic outfit that looks normal. There is, however, strangeness if the cloth is fitted while render settings are under SF. Switching to FF before fitting the cloth doesn't come up with any strangeness — no idea why but it has worked on two files okay. So work around seems to be fit cloth under FF and then select SF before rendering rather than the other way around. Only other downsides I've noted so far are

1. (on Macintosh BigSur) PP12 takes a long time to quit.
2. The materials room is really slow to change things when using HDRI
3. When rendering in SF and quitting after a quarter way the auto post work gives a very good quality finish
4. Dynamic cloth doesn't like working under SF selection (haven't tested this cold from start up)
5. Selecting Poser Manual from the menu doesn't seem to open it up... Other than that PP12 is a huge improvement and the team deserve a congrats on their work. Many thanks to Ghosthip2 for the HDRI primer :)