A busy queue does not need to use every bit of your connection. FID gives you two useful controls: a per-download speed limit and the maximum number of simultaneous downloads.
Start with fewer simultaneous jobs
If everything feels slow, reduce simultaneous downloads in Connection settings. Your queue stays organized, and fewer transfers compete with the rest of your network activity.
Use a limit for a specific file
When adding a download, set its limit in KB/s. Zero means unlimited. Remember that the limit applies to each download, so multiple active files can add up.
Do not chase connection counts
Parallel connections can help with some servers. With others, more connections bring no benefit or create more failures. Begin with defaults and adjust according to actual behavior.
Read more about speed limits and parallel connections.