Found an older answer, finally! Seems like features will be downgraded if using different (and lower) types of Deco mesh devices.  Hope this helps other folks searching for the same topic.

Note: When building a Deco network with different models, some features will disappear if one of the Deco units doesn’t support them. For example, if Deco M5 supports Fast Roaming while Deco M3W does not, then the Fast Roaming feature will disappear if you add the M3W unit into the M5 network. But don’t worry, these features will be added in future firmware updates.

Source: https://www.tp-link.com/en/support/faq/2248/