Hi Lee,
John is correct in that usually preceding/following refers to the direction on the sky. It is particularly useful to record this on a planetary observation as it unambiguously establishes its orientation. It is convenient that the majority of planets rotate in a such a direction that celestial and planetary are broadly the same although the axial tilt may put them out of alignment. The extreme case is Uranus which ‘rolls around on its side’ and can even appear face on.
With regards to Venus I always report with celestial preceding not planetary.
There is one exception to all this. If you are using WinJUPOS software, for example to create an image measurement file, then that software uses planetary preceding and the Venus ‘P’ side is on the opposite side to other planets such as Mars and Saturn.
David.