If you are talking about data inside of packets such as Facebook photo's, bank account balances ... (or anything naughty...)
NO, we do not and can not see what's inside. And will not even if it is possible.
Firewalla operates by ONLY looking at the packet header, we believe using that piece of data, we can 'estimate' the activities.
The firewalla device will see the IPv4/IPv6 packet header. (bunch of numbers) And mapped DNS addresses clear text and a bunch of other metadata.
The firewalla App will see exactly above.
The Firewalla Cloud will see mostly hash data. Something like this: