Yeah tweaking hell is real, it's hard to work out the optimal setup without going through a whole lot of cable management nonsense - and then for it to not be what you thought or slow and uncomfortable due to something you hadn't considered.
A friend said the same about raising the stack and initially it had me thinking. Certainly it seems popular and fast for TT/Tri bikes. Then I realised the difference - the contact point on a TT bike is the elbows, whereas on the road bike it's the wrists. Angling the extensions up on a TT bike doesn't change the angle of your back because your contact point (elbows) stay where they are; on the road bike a raised stem pulls everything up including your shoulders and head. Also on a TT bike the torso position is likely pretty good already, the marginal gains from stack height are more about getting the shoulders in and forearms hidden in front of the chest. On the road bike, most of the benefits are still coming from the lower shoulder and head height / flatter back.
My plan is to take the bike / geometry to a bike fitter and get them to replicate it, and also take the 2 bars I plan to try with me. They can then tweak stem length and angle until with my hands on the hoods and wrists on the bar, my upper arms are vertical, forearms horizontal and back as flat as possible.
Hopefully (fingers crossed) what we work out during the fitting will perfectly match the position once the new cockpit is on the actual bike.