Would that make my last nand back up harder to use because of the fuse count with higher OFW?
Indeed. Also, you'll be missing logs that were sent after you made your backup, when your Switch connected to the Nintendo servers. While that backup is useful in case you brick your Switch and there's no other backup available, you're most likely to cause mismatch between the logs in your console and on Nintendo servers.
For NAND backup usefulness as far as avoiding ban goes, I'll quote the steps from this thread:
The correct process for trying to avoid a ban are as follows:
- Make a clean NAND backup before doing any other hacks/CFW/homebrew using Hekate including boot0/boot1 and raw eMMC GPP (which will become a rawnand.bin)
- Perform any and all hacking offline with the Wi-Fi settings deleted and Airplane Mode to prevent accidental connection to Nintendo Hotspots (think 3DS Spotpass)
- Restore the clean NAND backup as well as boot0/boot1 prior to going online
- Make another NAND backup as well as boot0/boot1 at this point since your NAND has made permanent changes while connected to Nintendo's servers that are not present in your original NAND backup
- Repeat steps 2-4
With that being said, I'd definitely recommend that you remove all saved WiFi connections on your console and make a NAND backup afterwards. Make sure that your console never goes online (or, more specifically, connect to the Nintendo servers) after that. However, if you're using your sysNAND for playing legit games online, then you probably don't need a NAND backup to be made every so often as your console will be connected to the Nintendo servers all the time. Having one clean backup in that case is probably enough in case your NAND goes bad or corrupt in not so near future. Again, restoring such NAND is risky due to the log mismatch so keep that in mind.
As for the fuse count, you can still restore the old backup, but your console probably won't be able to boot. I'm no expert but I believe that you'll be able to boot into Atmosphere CFW on your sysNAND regardless of fuse mismatch, after which you can update your console via Daybreak to whichever firmware you want. Again, remember the log mismatch whenever you go about restoring backups.
If I make a new Nand back up before updating my emunand is it doing it from sysnand ?
Sure. I've made my first backup by following
this guide.
Is the a specific type I need to get usb c - usb
It is advisable to use an A-to-C cable (for Windows, if using TegraRCMGUI) and USB OTG adapter (for Android, if using Rekado).