Won't removing the Microsoft key prevent UEFI option ROMs from PCIe cards from loading when Secure Boot is enabled? Is it even possible to install firmware con

Won't removing the Microsoft key prevent UEFI option ROMs from PCIe cards from loading when Secure Boot is enabled? Is it even possible to install firmware containing an oprom resigned with a custom key onto, say, a modern Nvidia GPU, without the entire firmware bundle being signed by Nvidia's own key?