Thank you for your question.
Experience of pain for any individual for any procedure can vary widely. I will answer based on the average pain experience of my personal patients although your experience could certainly be different.
In general, operations that involve cutting or manipulation of the muscle to be consistently more painful that those that do not. For example, breast augmentation under the muscle averages more pain than augmentation above the muscle. The addition of any muscle tightening to your procedure will increase your pain post-operatively as well as your recovery time.
A mini tummy tuck is still a significant procedure in that it involves the soft tissues of the entire lower abdomen and you have a long incision to heal. It is a smaller area than a full tummy tuck and thus associated with less pain in general, but it is likely than you will feel pain for several days followed by general discomfort and soreness for several weeks.
There are several strategies to help with post-operative pain including long lasting numbing agents (Exparel) as well as paid medication and muscle relaxants. I have found these to be of great benefit to my patients.