Getting a second drive just for windows I think is a good approach. If you were to do so, it’s important that you remove all other drives while installing windows, otherwise the Windows installer will put its boot files into whatever existing EFI partition it finds.
To have a local account, I use Rufus to setup the usb installer in a way that it automatically creates the local account, and it can also disable the secure boot and tpm requirements from the installer if you want. Though I think rufus is a windows program only. I know there’s the “OOBE” approach for the local account, but I haven’t done that before. That could be an option too