Bike frames are available in different angles, and angles are impossible to measure, so when comparing or measuring up bikes, I use offsets in [x,y] from the bottom bracket.
If your mark the BB position on the top tube, then measure back to the saddle, the exact seat-tube angle is not needed.

Sometimes experienced fitters may suggest a change to your riding position. Even top pro riders can have their positions modified. This is probably the most significant "deliverable"