Hello Dezso,
Certificates added to the TrustedCAs are used for authenticating the transportation between your PI system and 3rd party by using HTTPs i.e, through SSL.This is for Transport level security.
Separate keystore view is usually created if u want to sign the message and use HTTP authentication. Usually this is done using the Private key. This is known as Message level security.
This does not change based on the adapters. For all the adapters it is the same functionality.
Regards,
Nitin