Being interested if changing the setting "Data row limit for non-delegable queries" could improve performance for delegable queries on a SharePoint list, I decided to create an app for this similar to one I create for this blog post.
I used a list with 50.000 items. It contained an (indexed) column with only 3 items containing a specific value. I filtered on that value using '='. The results were put in a collection. The query was ran 20 times with an interval of 60 seconds.
I ran the app three times, everytime with a different value for the setting 'Data row limit for non-delegable queries'.
I noticed no significant differences meaning imo this setting has no performance impact on delegable queries. O well, it was worth investigating
Below are screenshots of a chart (see mentioned blog post) containing the query times for the three different values.