I want to lift like a competitive power lifter, and body build, and run marathons, and...
My people lift with a specific style because they see someone else doing it, or want to pretend to be a power lifter, or a crossfitter, or a weightlifter. Theres two categories of people those looking to improve their health, their aches and pain. Then there are those who actually compete in weightlifting, power lifting, crossfit, bodybuilding, strongman, and endurance athletes. Your workout should reflect your sport, or your goals. Don't try to be good at everything, stick to what YOUR body needs.
First I want to go over the open scissor position. Go into any gym and you will see this posture in every lift. The position refers to the positioning of the diaphragm and the pelvic floor. Think of these two structures as the blades of the scissors. open scissor position is when both structures are angled upward, like a pair of open scissors. The spine is the point of access for these scissors. This position creates a weak connection. The core becomes unstable and decreases overall performance and strength.
Your gonna say, then why is it that I am stronger when I do that. Well you've done it for how long now, and your body is compensating for this lack of stability with other muscles. Its only a matter of time that you injure your self, or have re-injure something.
In order for the core to properly function, the diaphragm and the pelvic floor needs to be parallel. This is the most stable position for your core, and low back. The ribs should be set through out the entire movement. At first your strength will be decreased, but once you strengthen your core, your PR (personal record) will continue to be broken. Not to mention you will have less injuries along the way. I have seen this position many different lifts, the most common is the squat, bench or chest press, deadlifts, and any over head lift.
Power lifter do this in their bench press because it gives them a mechanical advantage to lift heavy weights. The moment arm is decreased, this allows them to bench press much more weight than the average person. Don't forget that these are trained athletes, they have been working on strength and technique for years. So don't confuse this with proper lifting for the average person.
For the average joe who does not compete be smart about lifting, work on your weaknesses to improve overall health and durability. If you see a new lift, or want to learn a specific style, seek out a professional (a true professional, not just some fitness person on instagram claiming to be a professional). Find someone who has been certified in the specific style, or find a reputable strength coach.
Here are is a small list of groups who teach proper lifting technique:
Kettlebells: Strong First, RKC
Barbell lifts: Certified strength and conditioning coaches, at least a level 2 crossfit coach, Strong first barbell cert.
Weightlifting: USA weightlifting coach
Core stability: DNS practitioners, followers of Stuart McGill and Craig Liebenson, some pilates and yoga teachers who DO NOT teach to suck the belly button toward the spine.
Powerlifting and strong man: Actual competitive power lifting and strong man coach