Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Default Texture Width
PREF_PM_WIDTHParameter: Default Texture Height
PREF_PM_HEIGHTParameter: Default Channel
PREF_PM_CHANNELParameter: Photoshop Path
PREF_PM_PSPATHParameter: Work Path
PREF_PM_WPATHParameter: Mode
PREF_PM_MODE