RMAN configuration setting and behaviour

Hi,

Few questions on how RMAN configuration works. Here is the scenario:

Full backups of database and archive logs are backed up to a disk( folder on DB server). This folder is backed up to tape daily. The retention period of tape backup is 90 days and files are never deleted from this folder by any other means We have to delete them using RMAN

1) If I set "CONFIGURE RETENTION POLICY TO NONE;" and "CONFIGURE ARCHIVELOG DELETION POLICY TO NONE;" at RMAN config at DB level, can we change retention policy in RMAN run block to say 30 days like below. Intention is to set configuration changes temporally in RUN block