Thanks for your help. It seems to be working really well so far.
To also quickly contribute to the topic, I use the below settings with bandwidth of 1000/40:
Download Threads: 10 (not sure here)
Upload Threads: 5 (not sure here)
No background I/O
No Download Throttling
Upload Throttling: 30mbps
Upload Threshold: 1 MB or 5 Minutes
Minimum Download Size: 50 MB (not sure about this)
Prefetch Trigger: 1 MB (not sure here, have some small files like books/comics, so I thought I should put a smaller value here. Also, maybe the video would start sooner)
Prefetch Amount: 300 MB (not sure here)
Prefetch Time: 10s (not sure here)
Basically, I am not sure if the prefetch is optimally configured.