Hello,
If you are a partner - it might be best to reach out to your Cisco AM or team to understand the offerings better. I would not want to sell a product that I have little knowledge in.
A-FLEX-DEVICE is the SKU for device registration for room kits. There are multiple SKU types, and for only 16 accounts, you should look at the A-WX-* or A-SPK-* SKU's. There are multiple types and you would want to make sure you are choosing the best one for the customer. A-FLEX-* would need 250 minimum user count.