There’s nothing about any of that in the documentation.
Since DBIx::Simple does nothing extraordinary, I assume it works with Apache::DBI no differently than any other piece of code that uses DBI naïvely.
I can’t see that it uses connect_cached;
it does expose the database handle via a getter, but there’s no way to set it or to supply your own. Supplying your own would make this and more things possible; that might make a good feature request.
As for prepare_cached, it actually uses its own caching scheme for statement handles; but it does not use prepare_cached. I don’t know what the motivation behind this is, so there may or may not be a good feature request to be made here.
Makeshifts last the longest.