A:
The size of the font will largely depend on the features included with the specific App. Nook may have one maximum size, and Kindle may have another.
Since Samsung doesn't produce those Apps - although they are hosted on our Android systems - those specific App developers would be the best way to find out that information.
Many developers may also have a reviews section or will take requests and suggestions for features, so the Apps developers are the best people to ask.
Thanks for your interest in Samsung products.
--Mr. Samsung