For max cooling performance in the 1000d, you would need to have 2 x 480 (58/60mm) radiators at the front and 2 x 360 (58/60 mm) radiators at the top, all in push/pull.
The above combination gives the best radiator cooling, as well as the most silent fan operation, and all fits inside the case, without having to modify any of the rails.. It would look the same as the first pic in your post, which is the one Corsair built.
Using radiators that are thinner then the above ones, will result in less cooling performance. 60mm radiators in push/pull give the best cooling performance, over 30mm or 45mm radiators.,
With all the hardware you are putting into the case, especially the 4 x 3090 GPU's, you will need the thicker 60mm to achieve the best temps.