How many Memory Cards are used with both "Tea Dragon Society" and "Autumn Harvest" card games?
A question about combining has been asked on BGG and the designer, Steve Ellis, answered as follows.

Please feel free to mix and match Memory cards as long as you use
select the appropriate number for your player count as referenced in
the Autumn Harvest setup. For the Market cards, shuffling these all
together is perfectly acceptable or you can customize the Market deck
as you see fit with cards from one or both games as you desire.