There are a lot of regurgitated comments such as hip angle and power output. Hip angle is set initially in the studio based upon flexibility tests. ERO set my hip angle at the same position as most Euro pros. Making sustained power at an optimized aero position, IMO, is about time in the saddle and strength and adaptation. My wife who has a national 20k TT record and 3 world track records makes the same power in her ERO position as she does climbing on her road bike. She rides her TT bike a lot.
Head and neck position is influenced by the width of the pads. In general, the closer one puts their elbows together and rounds the shoulders, the more difficult it becomes to keep the head down and still have forward visibility. I attended a aero pursuit seminar at VSC where we worked on head position and many times the pads had to be widened to get the head down.
This is very individual. We were in Aguascalientes in August when Lambrey set the sub 4 minute pursuit record. My wife set but yet another WR. Lambrey’s morphology is perfect for the pursuit position. He is a genetic freak and just hits every metric perfectly.
I have long arms and legs and wide shoulders. Great for tennis not so much for pursuit.
Back to hip angle…I tested various hip angles and found that I had about a cm of not much change in CdA around the ideal set point. So I set my bars at the higher set point. Even if I go up a 1/2 cm, there is not much change in CdA and I can see much better and I can relax my neck more.
My point to all this is there are a lot of variables to optimize and some, like hip angle that get a lot of discussion, in practice, are not that big a deal. The more relaxed I am, the more power I can make. If I carry any tension, my power suffers. YMMV.