Since in your head canon, fluffies are programmed creatures, it’s fairly easy to figure out what phrases they should know if you consider their original design specification (companion toys for small girls) then add a large dollop of corporate greed/marketing.
You’ve got the basic ‘demonstration’ mode to encourage the customer to buy them, so stuff like “Hewwo nice mista/wady! Hab nyu homsies fo fwuffy?”, and catchphrases like ‘Fwuffies am fo huggies and wub’.
You need some basic terms for interactions and actions (e.g. ‘huggies’, ‘upsies’, ‘poopies’), objects (‘fwuffies’, ‘nummies’, ‘nestie’, etc) and programmed ‘cute’ behaviour (e.g. ‘espowing’).
Since they’re going into a family environment, they need terms for things that a family might have, for example other pets (e.g. ‘barkie fwend/munsta’, ‘meowie fwend/munsta’).
You then need some customer instructional terms like harm avoidance (e.g. ‘wawa bad fo fwuffies’, ‘bad upsies’), damage to the unit (‘wowtest huwties!’) or ‘this unit is now defective and needs replacement’ (‘Wan die’).
If you’re interested in the subject, OculusFluffy’s Fluffnation series explored Fluff speak being its own distinct language, much like Jamaican patois.