So if I am in "AMS S" and starting Daybreak in the homebrew menu, I will update my sysMMC and burn all the fuses, which prevents me from downgrading, right?
Not exactly.
The fuses are burned at console reboot.
At console boot, the console launches a "payload booter" to load horizon.
This is the "payload booter" which verify if the current fuse number matches the required burned fuse of the Horizon's firmware version it will load.
If the firmware requires a higher burned fuses than you currently have, the payload booter will burn them before booting Horizon.
If the current burned fuses are higher than the requested number of fuse, then the payload refuse to boot Horizon.
If you use Hekate, or fusée primary as your payload booter, it does NOT burn any fuses.
only "stock" (official, no patches) payload does.
as long as you use RCM and a homebrew payload, your firmware fuses are not burned.
the first time you'll launch your console officially on sysMMC without using RCM, it'll burn them.
I updated the guide to include the burning fuse step.
If you ever want to downgrade, I think Hekate let you check how much fuses are burned, and you can see how back you can downgrade if you want to boot "officially". because, remember that booting with hekate or CFW, it doesn't care how much fuses you have, whether it's too much or not enough.
The only issue you can have with mismatching fuse number is the "game card" slot fuse.
Just one more question: when do I need the "bootloader" folder of the sigpatches.zip-file?
This is a folder used by Hekate.
It contains sig Patches for the fss0 boot method (instead of fusée primary boot method)
The patches are now bundled together, whether you boot with hekate fss0 or (hekate+)fuséeprimary, both patching method are in the same zip file. The "bootloader" folder is not needed if you don't use fss0 boot method. Whether you copy that folder and its files to your SD card or not has no consequence if you use fusée primary. do like you prefer, keep it or not.
edit: oops, to late
edit2: I added extra info.