Lats are a major player in a lot of issues I find.
I mean, they run from the posterior iliac crest up the the crest of the lesser tubercle (and some fibers may even attach onto the inferior angle of the scapula in some people).
Knowing that, the lats can have an effect on upper crossed syndrome because they are interal rotators of the shoulder and when overactive, can exacerbate that posture. As well, because of their pull on the posterior iliac crest, they can work as a force couple with other muscles to anteriorly tilt the pelvis. This can be seen occasionally when people raise their hands up overhead and they arch their lower back as well to get the full range of motion (this may or may not be the cause of short lats as it could be other things though).
As well, if the lats become adhered to the teres major (or in people that have the lats attaching onto the inferior angle of the scapula) it can make for a "sticky" scapula and prevent proper scapulo-humeral rythm.
The lats are fed by the glutes on the opposite side via the thoraco lumbar fascia (think how we do things in opposition with regard to our lower and upper extremity) which, if the glute is weak can lead to an energy leak and overactivity of the lats and other shoulder muscles (you can see this sometimes in pichers or overhead athletes who have either weak core or weak lower extremity and have to generate more torque through their arm, creating either shoulder problems or elbow problems.
I work the lats prone using pincher compressions through the lateral edge. I like to use some of the ART stuff, especially up near the attachment and where it passes through the axila as there are a lot of tissue running through there that can get "glued" together. Also, side lying I will use sometimes as well.
Patrick