Encryption only applies to terminals (portables, mobiles etc). Basic encryption is usually good enough to avoid other radios or scanners from listening in. Advanced encryption is usually for somewhat more secure requirements than the average user will ever need. Also, there is no additional data overhead for basic encryption.
To also protect the repeater access one could use RAS (Restricted Access to System) which also requires the correct key to be present in any intended user terminal, and prevents any other radios from even listening in. However I don't think the 8300 being an older model ever did support it. Maybe with a Firmware upgrade.
