“Coming this Oct 2020”:
A Key-B (or Key-B&M) SATA M.2 drive can be internally installed. I would expect 180MB/sec, sequential write speed. Has passive cooling by the aluminum case touching the CPU.
Power supply not included.
PS: I personally have an Argon NEO Pi 4 case, and love it. I’m a satisfied customer, and I’m not paid in any way to promote any of this.