In PRPC 6.x versions, interpretBoolean(java.lang.String aBooleanString) method is used to compare. This interprets a string as either boolean true or false. If the string matches "1", "-1", "true", "on", "yes", "t", or "y", the return value is true. Otherwise, the return value is false.
In Pega 7.x version, comparison of Strings is done using compareTwoValues(String lValue, C2VOp comparator, String rValue).
There is no such functionality or feature to get you the impacted rules. You will have to check all the when rules used in the system to see if you are doing any string comparison.