Boot-loader Flashing vs. using Flashfire

(originally posted in the flashfire threads, but it was suggested I post here)

My apologies if this has already been covered (I could not find an answer in searching)

I appreciate that it can be dangerous to use flashfire to flash the bootloader partition and that one should use fastboot. My question is:

If I download a FW package and the bootloader has changed, what happens if I flash to the kernel, system, cache, vendor etc... and do not flash to bootloader and radio? Will the flash fail; will the phone soft brick; will nothing happen and I can go merrily along?

The question derives from this: If the phone can become unusable with a mismatched bootload and radio to the rest of the images, it would require to unpack the package and check for a version prior to flashing other partitions (so I assume). If I go that far, would it not be easier to not use flashfire and simply manually flash the required files when updates are available?

Thanks

N6, unlocked and rooted (previously always updating latest patches and rerooting myself (using TWRP), but wishing to try flashire)