You did not mention where you do backup. All of this needs to be part of a complete plan.
This is. what I do (your mileage may vary):
- Single internal drive is SSD for max speed and reliability compared to a HDD or a hybrid fusion drive
- Internal SSD is for boot/MacOS/apps/caches (and little else)
- Large external RAID 0 pair of HDD connected via TB3 contains documents, pictures, music, videos...etc.. It also contains my LR catalog backups
- External SSD connected via TB3 contains my Lr catalog along with all the previews....etc.
- Large single drive connected via TB3 is owned by Time Machine and makes backup copies of the entire file system
If I had income based on my catalog and raw images, I would like also have an online backup such as Backblaze and maybe rotate backup drives off site to a bank vault. Each person has to decide how much they value their images and what expense they will incur to protect them.
You will to either let Lr Library move the folders to the new drive or, once they are moved you will have to have Lr find them again on the new drive. Suggest you do the move via LR......only have a full backup.