I would put the 2 2TB in RAID 1 and use an external server as back-up.
I was not aware of a special program to change the location of the vhosts folder.
I guess that moving is supported by Plesk.
But why move to /home ???
That's a special folder as well...
You could create a /vhosts which would come on the SSD and move it there with the command
@IgorG suggested.
The /home folder would then stay clean and only have folders for users you create for the Linux system. I have several....
With mount you can control all the locations without the program knowing anything about it.
I had a similar system where I wanted to speed things up by moving the SQL database to the SSD. I used mount in /etc/fstab for that.