I have noticed that the typical db shoulder press starts from a position where elbows and arms(including dumbbells) are perfectly parallel to the body in most images I see online, looking like the end of a Cuban press almost. Now I notice my shoulders feel more comfortable at 20-30 degrees from body. Actually I almost find it impossible to be parallel without forcing scapula to retract almost too hard, and my rotator cuff starts hurting. Is this position normal and places same amount of stress on all deltoid muscles or is something wrong with my rotator cuff?
I agree with @DaveNewtons comment. This is likely due to shoulder mobility issues.
To answer your question quickly. 1. "Is this position normal... or is something wrong with my rotator cuff?". Yes, this seems be the norm today. Not everyone possess good shoulder mobility and I think this is likely due to a computer mouse (right hand). There is nothing "Wrong" with your rotor cuff, but you want to have healthy shoulder mobility.
"and places same amount of stress on all deltoid muscles". No bruv, if you want the shoulders of a Greek-god you need to hit it from all angels.
Whether you are training for aesthetics or Olympic lifts shoulder health is important. See this video for something I "try" to do on every warmup.