When referring to the browning and blistering of pizza cheese, we're looking at the number & size of the blisters, as well as the colour of browing - there is a whole range of blistering and browning.
However, there is no wrong or right amount - it all comes down to the personal preference of the consumer.
The goal is to establish the optimum amount of browing and blistering your customer / consumer prefers, and making a consistent cheese that meet those parameters.
** Refer to the article attached for more information on some of the factors and methods to control cheese browning and blistering.