I had an aero bike ( systemsix ) and a topstone alloy shimmano 105 (2019/20 model I think? before they changed the name to apex 1 2 3 4 ) at the same time. I used to ride them both on the same 10 and 20 mile loops.
When I put the road wheels from the aero bike on my gravel bike the times did not change much at all in stop and go commute traffic.
I have a 37 mile loop route that I optimized with less lights, going clockwise ( right on red etc..) on this route there's 1 to 2 mph difference in avg speed which is a lot.
I have had bad luck with gp5000 and flats. I still use them when I want to go fast but I would not use them as my I have to get work tire.
My day to day tire is tubeless gravelking slicks in 32mm. These I ride on gravel and road all time. I am not sure how that compares for speed to your schwalbe marathon supreme.
Aero clothes and body position make a night and day difference when going over 15 mph / 24kph.
kind of embarrassing :-) I used to wear just normal clothes while biking. BF helped me out. ha-ha
What to wear @ 20+ mph?