Does the ASRock DeskMini X300 prioritize SATA bulk storage over a second NVMe slot?

Yes, the ASRock DeskMini X300 has one M.2 NVMe slot and two SATA 6Gb/s ports for 2.5-inch drives, with room for two 7mm-thick drives in a single bay. If SATA bulk storage matters more than a second NVMe slot, this layout wins.