Operate Away from the Margins
There is no such thing as the perfect strength. Every individual has different preferences and thresholds in regards to a minimum and maximum enjoyable strength. Therefore, it is best to operate away from the margins, in a zone where the majority of people can enjoy the coffee. Differences in regional preferences and brew method styles can create your margins. At any TDS, the strength-flavour profile can be used to navigate to a balanced and cost-effective intensity level appropriate to your brew method.
The best strength for espresso is widely debated and never sees consensus because the possibilities are so varied.