The role of the principal is to get people to play as a unit. That entails supplying bowings and articulations, dynamic suggestions if not given by the conductor, to lead rhythmically and be the basis for intonation in the section. If you need to sit at an obtuse angle to do all that, go for it.
Generally speaking, the conductor will be the first source for articulation, dynamics and phrasing, but absent any feedback from them, the principal player might offer some guidance. If you are asking for advice on how to be a principal, my advice is to keep the talking/showing ratio as small as possible.