CPU usage can increase linearly with the number of syncs running in parallel. CPU usage can also vary depending on the speed of the involved volumes.

If you have several syncs running in parallel, you can try to run them sequentially to reduce the amount of resources used at the same time. Some possibilities are:

• Combine sync items with a common parent directory. Set the parent directory as the source, then exclude it and add the desired subdirectories as included files. You can read more about this technique in Filters.
• Create a sync group, which runs all contained sync items sequentially.