This article gives some recommendations for configuration options to tune a migration. Proper analysis should be performed, but these general guidelines may help.
In general try to have the mailbox parallelism as high as possible (Office 365 Mailbox Parallelism), in order to process a broad width of archives.
Use Office 365 Batch Parallelism at 1. It is possible to have higher, but may lead to backoff errors. If, for example, the parallelism set to 3, and backoffs occur, go back to 2, and monitor.