Unless you are a very experienced orchid grower, ie. Growing for ten years or so, I would not recommend sphagnum moss by itself for anything!
It is too easy to pot the orchid too loosely. This negates using the moss to begin with.
It is too easy to pack the moss too firmly. This blocks water penetration which is not good.
So it is like the 3 bears story, too soft, too firm or just right. I have been growing orchids for 47 years and I am still reluctant to put things in moss.
Now Paphiopedilums are moisture loving, low light plants. In terms of their light requirements they like more light then a Phalaenopsis and less then an Oncidium.
These images are of my underlight set up. 12 hours on in the winter, 16 in the summer. They grow very well. Most are in 4" pots and are watered about every 5 days in winter, 3 days in summer.
I myself use a mixture of 50% seedling fir bark, 20% aliflor, 15% seedling grade charcoal and 15% seedling grade perlite. That is true for Brachypetalum or Callosum types.
With strap leafed slippers that bloom sequentially, I give the mix less fir bark and more charcoal and perlite.
I fertilize about once a month at half strength.