That's not a first time I writing about the problem! After Effects CC 2018 Optimization is just terrible while same Premiere version works great! I'm working with same video file (4K, 29 fps, 1 min length), and AE can't even play smoothly the file on the timeline. In addition, the rendering time (via Media Encoder) is longer X10 than Premiere rendering (rendering settings also are same!!!). All app settings are same and GPU support is on! So when I checked the resource monitor, I see that Premiere uses about 70-90% of the CPU, and about 40% of the GPU. AE is using about 5-10% of the CPU and 2-5% of the GPU. Please do something with the optimization! Thanks.
My system is: ASUS Prime X399-A
AMD Ryzen™ Threadripper™ 1950X Processor (16 cores) 64G of DDR4 RAM GeForce GTX 1070 8G