Getting an idea of maximum Solv is important to understand when you need to shift gears and target a different keyword or when to open up a new location. I always look at the best ranking competitor to get a sense of what the upper limit may be for visibility
queries with locations in them don't have the same solv bubbles, as outside the area google will consistently show the same profiles with little variation no matter where the searcher is.
if you did 'houston car accident lawyer' from NYC you would see the same from a search in LA
I recently did an analysis for a client that tracks two queries across 300 locations. I found that the average max solv's were not the same for the two keywords, meaning that it was inherently more difficult to rank for one keyword than the other.