In your case, bootloaders (both your existing Windows as well as your future Fedora) are not installed into the MBR of your hard drive(s). Your hard drive (GPT formatted) has one EFI boot partition (typically 100 MB), where each operating system places its bootloader. You already have that for Windows, Fedora will put grub2 into the same efi partition (and automatically mounts it to /boot/efi).
You need to make sure that during install you tell Fedora's installer to use the existing efi partition (select it and define Mount Point /boot/efi), and not to format it (or you loose your Windows bootloader).
That being said, if you decide to remove Fedora you still have the Windows bootloader on the efi partition. Typically, the BIOS lets you define the order in which the bootloaders are loaded. So after installation of Fedora, you want to select GRUB. In case you remove Fedora, you can go back to the Windows loader.
Grub will recognize the windows bootloader automatically. If that fails, you can use os-prober to add it (as described in one comment above), but that's a different story you can take care of later.
For now, just install Fedora, and make sure you use the efi partition without formatting it. (Your Fedora system, incl /, /home, /boot, and swap can go on a second drive, but your efi partition will be the one from the "first" drive.
it might not see the Windows from the get go, however to add Windows SSD to the grub menu is a trivial task. Just mount the disk and run os-prober.
You will have to set second disk as a first boot option in the BIOS, and no, it will not impact Windows boot loader on the first disk, even if you uninstall/remove the disk with Fedora. You just boot the disk with Windows, and that's it - it will boot Windows.
legacy or (U)EFI boot here?
UEFI boot.
Secure Boot?