Go under System Info > Hardware > PCI. Double-check the SLOT reporting for your PCIe boot drive. Make sure you're reviewing the correct drive for your boot/system drive.
Nothing about this looks too out of the ordinary. The random Boot OS X
partition is likely an old recovery installer, possibly from the original SM951 that was never wiped during initial setup. Really depends where this was acquired from and/or repurposed.
The only way to truly "clean" that up would be to clone to another drive (drive B), boot from clone (drive B), then completely wipe the existing drive (drive A), then clone back (drive B > drive A). If doing through CCC, you can re-establish a new Recovery HD partition during the clone back and it will ONLY create a recovery partition for the newest available OS.
Some partition tools may be able to address, but they are not guaranteed. The way recovery partitions interact with OS and tools varies greatly depending on what they're allowed to access and what physical drive they are booted from. Top level access is only available for external (non-system) drives for some tools.
I'm using EVO 970 NVMe via PCIe adapter (Angelbird Wings PX1) with 22.214.171.124.0 firmware as system drive currently with 10.13.6 17G5019. Attached is how it reports under Hardware > NVMExpress.