BIOS is on the motherboard, not a drive.
Assuming you are willing to reinstall from scratch again, just disconnect all but one drive---leaving connected ONLY the drive that will get Windows.
You want ALL Windows files on the same drive.
You can move the uefi boot parition with this software How to move the EFI System Partition to another drive? - EasyUEFI
There is no real issue with having it on the separate SSD. As long as you know where it is so you don't do something like format the entire SSD that does have the system partition on it and erase it by mistake. Luckily, it is extremely easy to rebuild, though.
In passing, and my apologies if this has been said before, you never install Windows with all the drives enabled as "boot drives" in the BIOS or Windows or the BIOS has a habit of installing everything on the wrong disk or splattering weird partitions and boot managers here and there. Always go in to the BIOS on first boot and select the drive you want the OS on as the ONLY boot drive option.
An issue that can happen with both drives connected when installing is If you then want to make an image of the boot drive to restore If needed at a later date, it will include both drives and will therfore require both drives when restoring it back which can be a pain, especially if you decide to restore to another drive.
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