I'm not 100% Knowledgeable on this subject, but overall Good Posture, especially Neck Posture in Today's world with everyone sitting down looking down on their self phones, is amazing and important for overall health.
It optimizes the function of the nervous system, and entire body.
It helps with Hormones, as well as Body and Skull Symmetry, and helps promote better Facial Growth and development from what I've heard Mike Mew Talk about, as well as many others.
Chin Tucked is ideal, but isn't practical for extended periods of times, just try to maintain a Balanced, Straight, Up Right, Natural Posture, and if you slacking off, always correct yourself.
If you have these Postural Problems, continued practice, as well as a Chiropractic/Osteopath, Mewing, NCR, Face Pulling, and Exercise, should improve and fix these problems over time, resulting in even,better and Quicker Results after breaking through a Plateau.
You could look up on YouTube Proper Posture, and Corrective Posture Exercises, Elliott Hulse has many good ones. There's also something called the Starecta method that relates to adjusting and Correcting the spinal and nervous system to optimal shape and function yourself, but I'm not too familiar with it.