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It depends on what you want to do/see. Particle concentrations in 2d-axi systems aren't always easy to interpret.
Adding more parcels and randomising the starting point changes the injection: it's different and I can't say if it's better.
The 30-60 degrees comment is relating to modelling a 30 degree sector, ie a 3d model. This removes the problems of whether the injection mass weighting changes the concentration as the inlet can have a uniform injection as the facet areas are actually there in 3d. Too low an angle gives a skew cell at the axis, too large an angle means you use too many cells. Given swirl and gravity tend to feature in many models I tend to run the full 360 degree nozzle.