Don't think that there are any key performance indicators (KPIs) for sex. The essence of sex is not about performance, but about pleasure! So, let's talk about "key indicators of pleasure".
A wonderful sexual experience stems from the appreciation of the experience itself, rather than the execution of "correct" behaviors. It is about feelings. Therefore, what you focus on is not quantitative KPIs - frequency, duration, the number of orgasms, etc. What you focus on are qualitative KPIs. These might include:
How do you feel?
Is the feeling mutual?
Do you feel there is a connection?
Do you feel it now?
How do you think of yourself?
Can you express yourself freely?
Do you follow each other?
Are you currently enjoying this experience?
Will you feel better after doing this?
Does it have the ability to enhance the joy, satisfaction, happiness and fulfillment in life?
These indicators cover a wide range. I believe you have many more specific indicators that are closely related to your personal sexual orientation. Therefore, I suggest you think about your own KPIs. If you have a partner, you can have a relaxed and creative discussion together to clearly define your common "key pleasure indicators". Then take action!