Looking forward now to having it built with Rival AXS. I will use a combo Mosso stem (integrated cable routing) + aero bards till I figure out whether I wanna go with an integrated handlebar or not. I always like rotating the bars a bit pointing up if that makes any sense.
The only issue of doing non-integrated bars first, (if you plan on doing integrated later) is that hydraulic hoses still have to be cut to length. Unlike semi-internal frames, there's no leeway slack on hose length with internal cabling. You can always redo the brake hoses if you go integrated, but that's just extra work!

As for me, I like messing with spacer height, stem length, bar width, etc. I know a cyclist who keeps going to the bike fitter due to hand discomfort, but there's only so much you can do with an integrated bar setup. These fitters are just fleecing him of cash when it really comes down to bar width, stem length and spacer height to get optimal fit. The best they can do with his setup is raise/lower or tilt his shifters!