Three recommendations that the administrator can make to reduce the file size of full data exports are:
Reduce the amount of objects per export. By selecting only the objects that are necessary for the backup and excluding the ones that are not, you can reduce the number of files and records that are exported and decrease the file size.
Deselect 'Include images, documents, and attachments' in the export. By unchecking this option, you can exclude the files that are stored in Salesforce as images, documents, or attachments from the export. These files can take up a lot of space and increase the file size significantly.
Keep deleted record counts to a minimum. By emptying the recycle bin regularly or using hard delete options, you can reduce the number of deleted records that are included in the export. Deleted records are still counted as part of the export limit and can increase the file size.
The other two options are incorrect because:
Requesting a backup file every 5 days does not reduce the file size of each export. It only increases the frequency of exports and may cause more storage issues.
Unselecting the recycle bin in the object export option does not reduce the file size of full data exports. It only applies to individual object exports and not to weekly or monthly exports.

To use outbound change sets, a user needs to have the Create and Upload Change Sets permission on their profile or permission set. This permission allows users to create change sets in a sandbox or Developer Edition organization and upload them to another organization. Reference: https://help.salesforce.com/s/articleView?id=sf.changesets_create_upload_perm.htm&type=5