The flavor really depends on how you do it. Sour mash isn't as much a flavor, as a time-honored distiller's technique.
The sour "backset" or leftover slop from a distilling run is returned to the grain fermentation.
It keeps the pH consistent from lot-to-lot (makes yeast happy), and conserves water.
The distilleries will use at minimum 25% of the backset from previous runs in subsequent batches, which creates a "Sour Mash", something they can then legally use for marketing purposes.
In the end, the flavors are a product of the master distiller's palate as he/she makes cuts between heads, hearts, and tails during the run, and then samples over time to determine the best casks to bottle or blend for sale.
That's probably why the master distiller for Jeremiah Weed gets paid less than the master distiller for Red Breast or one of the
Glens.