Hi Matteo and welcome to the community!
Do not forget to enable rotated drives
on the repository.
Skullblade wrote:Is correct create Copy job set with interval of 7 days and start time at 9:00 and start it manually for the first time on monday morning?
Yes, that's correct. The new interval cycle should start right after you switch RDX.
Also, review this thread with a similar approach for RDX Drives
Skullblade wrote:Futhermore RDX cartridge is 1TB and backup size is 800GB so is better clear the backup folder with pre-script or set force delete backup on registry?
You can perform cleanup of existing backup files prior each cycle, using the ForceDeleteBackupFiles