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).
Your prefetcher settings are effectively useless, and your minimum download is far too low. Your upload threads are probably too high as well.
Change your minimum download to 20MB, drop your upload threads to no more than 5. Use more reasonable prefetcher settings like a 20MB trigger in 10 seconds with a 500MB prefetch.
All of that should make a huge difference.