Yeeeeeeah I'm not convinced by the argument that a higher rake automatically equals more underbody downforce. It moves different parts of the car closer or further from the ground - i.e. front wing and front bib will be closer, but rear diffuser and rear wing will be further so downforce balance can become forwards biased. To maintain downforce at the diffuser requires a load of effort in the bargeboard area to induce vorticity to 'seal' the edges of the floor - prevent flow ingress raising pressure under the car - to that end induced drag around the middle of the car will be higher.
If you run identical front and rear wings with a high rake concept drag would be higher, just because the blockage of the car increases (marginally - we're talking a couple of points of drag), you also get a little benefit from the AOA of the rear wing increasing. Dropping the front wing increases the venturi effect so you can run a lower incidence for the same downforce, you may also get a thicker wake with a lower incidence, so again you have to work the bargeboards to prevent it impacting the sidepods and floor, though there may be a benefit over the suspension to the tops of the sidepods. You also change how much of the front wheel is shadowed by the endplate so again you have to work the air harder to reduce the front tyre drag by the same amount.
In the end I don't think the attitude of the car makes a massive difference to either total drag or total downforce, so long as the concept for the car is followed through from front to back. Mercedes run a massive wheelbase to both get the front tyres away from the LE of the floor, but also to increase the planform area of the floor. They get a benefit from their bargeboards and LE VGs which maintains downforce along the floor, the diffuser is also closer to the ground so their peak suction at the diffuser throat will be higher. But maybe they don't have the same positive front axle as the Red Bull (from aero so in medium speed corners) because the front wing is comparatively high up in the air.
"There is one big friend. It is downforce. And once you have this it’s a big mate and it’s helping a lot." Robert Kubica