[Samsung Galaxy S7 Edge Guides, News, & Discussion] ianmacd:
Well, I tried this (flashing to AQF7) at the weekend and lived to regret it.

Like you, I chose Firmware Package, deselected Recovery and performed the flash. Unfortunately, my S8+ booted into system, not recovery. In the process, I had evidently lost root, even though FlashFire should have rerooted the device afterwards.

I reinstalled SuperSU using TWRP, but then I noticed that the phone had lost all knowledge of its CSC. The well-known Phone INFO app listed the CSC ominously as forbidden.

The device was now in an unknown and unpredictable state. Several entries under Settings appeared twice in the menu, but with different content appearing, depending on which entry was tapped. This was no doubt a side-effect of the unknown CSC.

I went into Odin and flashed the remaining partitions, but after this the device started to spend much longer in the phone model screen that appears prior to the flashing Samsung logo screen. This meant that booting into either recovery or system now took much longer.

Once booted into Android, things still weren't quite right. The multiple Settings entries were still there, but now Do Not Disturb was also enabling itself every few minutes. On top of that, the device was now taking about 5 seconds to come out of Doze when I opened the cover, whereas previously it would illuminate the screen within one second.

Later in the day, a couple of well-behaved root apps caused a couple of random hangs that caused spontaneous reboots, so I knew something was seriously wrong.

I tried a full reflash of AQF7 from Odin, but this didn't help. The flash completed successfully, but I noticed that the download bar on the phone didn't make it all the way across to the right of the screen. A second attempt at flashing yielded the same result: delayed passage through the phone model screen, followed by slow wake-up and dysfunctional Do Not Disturb.

I tried a factory reset from the phone, but it failed to wipe the phone, booting instead back into the installed system. Wiping /data from TWRP didn't help, either. I could now reinstall the device, but the start-up delay was still present.

Eventually, I flashed from Odin again, but this time used the CSC file instead of the HOME_CSC file. This caused a full wipe and restored the device to a known state.

Bizarrely, however, that final Odin flash also had the very unpleasant side-effect of trashing my external SD card. TWRP said it wasn't formatted, Android itself couldn't even detect the card any more, and it took a reformat of the card on a PC to bring the card back to life. Unfortunately, the loss of the data on the card wiped out all of my FlashFire back-ups, leaving me with only the back-ups I had made to other devices and the cloud storage of Samsung and Google.

I've spent the rest of the weekend reinstalling the phone to get it back as close as possible to the state it was in before the weekend.

Given that both TWRP and FlashFire have now let me down in my attempts to upgrade the firmware on this device, I may just not bother to install any firmware updates after this.

The most important lesson I've learned is that even an external SD card can be affected by an Odin flash. It had been my understanding that this simply wasn't possible.