I can only speak from personal experience:
Deadlift- My favorite, the king of lifts! When I say a globally flexed position I'm talking about the fetal position archetype. Next time you're sitting down just imagine transitioning from your seated posture to fetal position. The deadlift is the opposite of this- you start in a flexed position, and then stand up perfectly straight. Make sure to learn how to properly brace before attempting this movement, or really any movement under heavy load.
Bench Press- My back muscles that are in charge of pulling my shoulder blades back and down are stretched out, meaning that my shoulder blades are usually much further forward and up than they should be. When I bench press the tendency is for my shoulder blades to roll forward. When bench pressing, you're supposed to keep your shoulder blades pulled down towards your butt and as close to your spine as possible. This creates stability and room in the front of your shoulder. When I bench press, I have to put in extra effort and use a light load to make sure can I keep my shoulder blades in the right position. This forward rolling is also associated with activation of the internal rotator cuff, which is bad- your rotator cuff isn't meant to handle that much load. So it's also very important for me to use a close grip and keep my elbows close to my body, maybe a 15-20 degree angle at my armpit in the bottom position.
Squat- I'm missing a significant amount of internal rotation at the hip. Sit in a chair with your feet on the floor, then without changing the angle between your upper and lower leg rotate your right foot up and to the right. This is internal rotation. External would be putting your right foot on your left knee. Part of my restriction is due to a lifetime of poor habits, but part of it is due to my hip structure. Think of a dog with hip dysplasia. This, combined with a tight posterior chain, makes it impossible for me right now to squat without compromising in some way. I find that elevating my heels slightly (often I'll just stand with my heels on 5lb plates) and pointing my toes slightly out (10 degrees) creates more room in my hip, allowing me to achieve a parallel squat. The danger of this is that without your feet flat on the ground straight ahead, you aren't integrating your lower legs into the movement in a natural fashion. Make sure to keep your knees 'not in' so that your arch doesn't collapse. A collapsed arch not only bleeds power, but the accompanying inward movement of the knee (valgus) can cause ligament tears.
Pullup- The same issue I have with the bench press where my shoulders roll forward under high stress. I usually don't have any trouble maintaining form as long as I consciously think about keeping my back straight and pulling my elbows down and back, rather than my head up.