Windows must be on the device you boot from. It is called the "C" drive.
It can be on either the hard drive, or the SSD.
The best use of a ssd is to have windows installed on it for performance.
If you just did a clean install on the ssd and can boot and run fine, then you are good.
When you install drivers for any device, they are installed in a windows sub folder on the "c" drive, namely your ssd.
Drivers are files which contain code needed to manage specific devices. They become part of what you load into ram when you boot windows.
Any other devices that are attached are fine.
The issue I was trying to warn about is where windows located it's hidden recovery partition.
It will try to locate that partition on a device separate from the "C" drive.
It is not large, perhaps 100mb.
The problem is, that it needs it to boot, so if you have it on a second drive, like your HDD, you can not remove the hdd, or wipe it clean for some other use.
That is why I suggested your clean install be done without any other drives attached. Then the install will have no place to put the recovery partition except on your ssd. That is good, and what we want to do.
After windows is up and running on the ssd only, then you can reattach your old hard drive with or without windows files on it.
You can delete them if you wish.