I’m using both on my test environment right now (still undecided if I want to go with embedded bbPress or external!).
You should be able to use BP’s internal bbPress forums by going straight to the BP forums slug.
By default, this is:
If your external bbPress install is the same as this slug, you’ll need to modify your BP forums slug to something else.
You can do this by adding this line in your wp-config.php:
define( 'BP_FORUMS_SLUG', 'somedifferentslug' );