Battery, keyboard, RAM and SSD have separate guides; its SSD procedure specifies a single-sided M.2 2280 NVMe drive.
What to check before buying
Storage
iFixit specifies a single-sided M.2 2280 NVMe SSD for the T16 Gen 3. A SATA or double-sided drive is not supported by that procedure.
Battery and input
The battery, keyboard and RAM each have their own guides. The battery guide distinguishes part numbers for the 52.5 Wh and larger options.