As @srcrist has said. Change the settings to:
Download Threads: 10
Minimum Download Size: 20MB
Prefetch Trigger: 5MB
Prefetch Forward: 150MB
Prefetch Time Window: 30s
Also, feel free to play with these values. Though, don't increase the time window (this is how long you have to read the "trigger" amount, so shorter is better), and the forward should be 75-85% of "Download Threads" x "Min Download Size" (this way, it should grab a lot of data in parallel, but not so much that it bottleneck's CloudDrive from doing anything else for that drive).