Yoga Sutras of Patanjali are a classical Yoga text in a Sutra form. It clearly states whom it is meant for. It is meant for a person who feels like that the life in the world has sorrow and he/she would like to come out of this sorrow completely. The Sutras layout a path for reducing the attachment to the world and then go into Samadhi state of mind. And, later also go into the liberation, which is a state where you would not be born again. The path laid out in the sutras is not an ordinary path and is not for students who just want to build health and fitness or get stress relief. It also does not have much to do with making the present life comfortable.
To perform the practices in that are laid out in Yoga Sutras, one should devote lot of time and effort. It is not like Transcendental Meditation of 20 min a day. Also, it has not much to do with Yoga Asana exercises or Pranayama performed for Health and Fitness. Also, it does not have much to do with Kundalini Yoga and Tantrism.
It is not my intention to say that the above practices other than those laid out in Yoga Sutras are bad or wrong, but they are not what are laid out in the Yoga Sutras. And, Yoga Sutras study is unnecessary for those interested in these practices. And, the study of these practices will not aid the practices in Yoga Sutras much. And, it will be stressful to do both the practices at intense level.