Need some help determining how panel positioning would impact my % efficiency

[ButchDeal]

To a first approx., for sawtooth arrays and for most panel tilts once self or adjacent panel shading is accounted for by adjusting the row pitch, the total annual insolation on a horizontal roof (or a horizontal array of the same area) is about the same as the total annual P.O.A. insolation that the max. size sawtooth array that can be fit on the same horizontal roof will see. Not perfect because of parapet shading, etc., but not too far off.

Kind of a no brainer if you think about it. Took me a long time to see it. Not sure what that says.

yep the insolation is the same but due to seasonal and shifting shadows especially since this is a pitched roof facing WSW (shadows will vary all across it or big gaps to compensate), the production will generally be less even with optimization for the south facing tilted array.
You further would have to deal with much more wind and odd snow loads.

Mounting flat to the roof would outperform, would have more modules but cheaper racking.

[azdave]

essentially, smoothing out 'their' end of it?

Pretty much. Having all those grid-tied solar producers peaking around noon when the utilities peak demand occurs occurs much later in the day is not much help to smooth their output ups and downs.

[J.P.M.]

yep the insolation is the same but due to seasonal and shifting shadows especially since this is a pitched roof facing WSW (shadows will vary all across it or big gaps to compensate), the production will generally be less even with optimization for the south facing tilted array.
You further would have to deal with much more wind and odd snow loads.

Mounting flat to the roof would outperform, would have more modules but cheaper racking.

Right on the 8/12 pitch, missed that. My bad.

As suggested, run PVWatts for that roof orientation and see what output might be vs. other possible array orientations for that roof. Some might look pretty bizarre however. Then, as you also suggest, there's external roof/support loadings from array orientations not parallel to the roof to consider. A few extra modules parallel to the surface would be what I'd design/check against for cost/hassle.