Execution precedence of column population using sequence as default and via before insert trigger

Oracle 19c single instance (non-CDB)

We are working on a modernization effort on an old legacy system. We are moving most of our Oracle Forms to Oracle APEX. As part of that process we are considering updating the underlying database to set the default on our primary key fields to the sequence number generator that we are currently using in the pre-insert triggers (select sequence.nextval from dual). We plan to leave the pre-insert trigger in place until we complete the modernization effort. Our question is what is the order of when the sequence number generator is accessed to get the next value. For instance, if