With CD Ripper Rev v15.1 on Windows 10 x64. Using multiple instances of CD Ripper with multiple optical drives.

*) Profiles do not remember the optical drive choice!! Profiles do remember the 'Set' destination but...
*) The ripper always saves tracks to the first instance destination, even if changed by 'Set' !!!
*) So if an instance is ripping a cd, starting another instance will cause it to scan that same cd too, because...
*) As soon as a disk is inserted, the ripper starts to scan it, and...
*) CD scans cannot be interrupted!

Some of this could be helped by working profiles, but in addition to the above issues they are clunky:
*) There is no way to update a profile! We must delete it and create a new one with the same name.
*) Unless you create new before deleting old, there will be nothing to copy from.
*) But if you don't delete first, you'll have two profiles with the same name and not know which to keep.

I think all the above is true, but I got tired of working through all this and went back to a single instance. That takes much longer but it's much less frustrating.

Conclusion: CD Ripper can technically support more than one instance - but you won't enjoy the experience.