Migrating from single disk to RAID5 – best way on TS464

Hi. I am running my TS464 with one 12TB disk. It is not enough so I plan to buy 2 more and end up with 24TB in RAID5.

From my perspective I see two ways of doing that:

Insert first new disk -> convert single drive to RAID1 -> insert second new disk -> convert RAID1 to RAID5.

Insert both new disks and create empty RAID1 pool from them -> copy data from single drive to RAID1 -> convert RAID1 to RAID5 using source disk as third one.

Way 2 imo seems better because during some time of the process I will still have backup on source drive, also one RAID conversion instead of two, so I would say less points of failure?

But I am not storage expert therefore if You have any advice I will read them carefully.

Regards.