Performance benefit we will get with external device for journaling for XFS?

We have 150 storage nodes, with 25 disks per storage node, all are HDD, with 1 nvme slot. HDD are XFS. How much performance gain would we see with an external device journaling, journal written to NVME. These nodes are write heavy work load, with around 2K requests for write per/sec. Size of these files are 4MB each.