As a '19 Comp Di2 owner, I agree that the bike feels fantastic, very planted on descents. Not a fan on the hover bars, just got mine swapped out for some narrower Zipp Service Course 80 Ergos. The Power is their most popular saddle, although they're meant for more aggressive riding position and my fitter said they typically are angled down. I prefer them for comfort over long rides because they do a much better job of supporting the sit bones than traditional shapes. Your cassette should be 11-34t unless you changed it.
I don't like the DT R470 wheels. I have Hunt Aero Light Disc wheels on my Al bike and they are way more nimble and aero, plus the low pawl engagement on the rear hub is a noticeable downgrade. I plan to get some Light Bicycle deep section wheels later, just living with the stock wheels so I can fully appreciate the upgrade.