Thanks again Tony. I do have the SSD assigned in System Preferences. I think I'll leave thie new drive plugged into the USB A jack. There does not seem to be any such thing as a female USB-C to male Thunderbolt 2 adaptor. The only option, as far as I can tell would be to buy a TB2-to-TB2 cable and a TB2-to-USBC adaptor (USB-C goes to the SSD). Kind of Rube Goldberg and rather expensive. And after all that my understanding is there will be no speed improvement.
Regarding using the internal drive for a second TM disk, I went into Time Machine and it shows the Seagate 3TB. Under that is "select disc" but it shows the Available Disks" as Seagate 3TB and ")ther AirPort Time Capsule". If I click "Setup" it shows my AirPort Extreme Base Station so I dunno. Off on a tangent, now I have to find out why the 2 AirPort satellites don't show up. And off on another tangent, I've had to use Time Machine a couple of times. As a former Windows user I'm extremely impressed with how well (and easily) Time Machine works.
MG: Your method sounds easier. I Googled how to make the SSD bootable. Took a little while. IIRC I erased it then chose to format with the correct Mac format. Had some trouble partitioning it but eventually after a lot of Googling got that done. Then it was pretty straightforward to migrate everything to the new "machine" (i.e. Samsung SSD). All seems good now. The 1.02 TB Fusion Drive still shows up but is not called Mac HD anymore. The new SSD shows up with a USB connection, as does the Seagate backup drive.
Does this mean you still haven’t installed macOS on the SSD? A safer way of transitioning to this new drive is to boot into Recovery (cmd-R), select (launch) Disk Utility, from the pull-down on the toolbar (to the left of “Disk Utility,” labeled view) select “Show All Devices.” Assuming you haven’t formatted the SSD yet and it’s blank, select the Samsung device and then click on “Erase.”
Select APFS for the format. Don’t encrypt. Give it a name (e.g. Macintosh SSD). (Do the encryption after installing macOS and then turn on FileVault.)
After this, you can run First Aid, but probably not necessary assuming the SSD is brand new. But it won’t hurt. Run First Aid on the container, and then on the volume. Quit Disk Utility and move on to Install macOS ________ (whatever Recovery decides is the latest version for your Mac).
When the installation is done, it will ask for the source for migration. You can use your present system drive, or latest Time Machine backup. When the migration is done, it will restart and you are all set!
I just finished erasing and installing Monterey on my startup drive myself, just a few minutes ago. I have done this so many times that I’m getting really good at it. Monterey 12.2 RC is not yet working properly, so I used Recovery to downgrade to 12.1 (21C52). I will wait for a stable version of 12.2 before installing it on this machine again.