Using old NAND backups, Newer Wii Brick Protection and How BootMii works?

I just have a couple of questions and some precautions that I want to take.

I have an older model Wii with BootMii as Boot2. A few months ago I've used BootMii to do a NAND backup while the system menu was on 3.4, and then I updated so I could play some newer games. I updated to 4.3, so I surmise that I skipped about 8 versions. Since I still have that NAND backup from 3.4 would it be safe to ever restore that backup should anything happen to my Wii since it's from a system menu so far back?

My other question is that my brother just got a new model Wii that I installed the homebrew channel on for him. Since his wii is can only install BootMii as IOS is there any other powerful method of brick protection since a BootMii as IOS can't really be accessed should anything happen to the console? If you could post a link with more details I'd appreciate it.

One quick curious question I have is when you install BootMii with the HackMii Installer, is there a difference between the "Install BootMii as boot2" option and the "prepare a SD card" option? I ask because when you select "Install BootMii as boot2" it seems to already prepare the SD card on that process?

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AdroitRef
I have an older model Wii with BootMii as Boot2. A few months ago I've used BootMii to do a NAND backup while the system menu was on 3.4, and then I updated so I could play some newer games. I updated to 4.3, so I surmise that I skipped about 8 versions. Since I still have that NAND backup from 3.4 would it be safe to ever restore that backup should anything happen to my Wii since it's from a system menu so far back?

You only skipped 2 versions [3.4 -> 4.0 -> 4.1 -> 4.2 -> 4.3]. Restoring your 3.4 backup will make your Wii 3.4 again and will not affect anything except that you won't have whatever was done after the backup (such as saves and the 4.3 update).

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AdroitRef
My other question is that my brother just got a new model Wii that I installed the homebrew channel on for him. Since his wii is can only install BootMii as IOS is there any other powerful method of brick protection since a BootMii as IOS can't really be accessed should anything happen to the console? If you could post a link with more details I'd appreciate it.

Priiloader is similar in that it boots before the System Menu and can prevent certain bricks (but not as much as BootMii). You can find that here.

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AdroitRef
One quick curious question I have is when you install BootMii with the HackMii Installer, is there a difference between the "Install BootMii as boot2" option and the "prepare a SD card" option? I ask because when you select "Install BootMii as boot2" it seems to already prepare the SD card on that process?

Preparing the SD card puts the BootMii files on your SD card (which installing BootMii does already) but if you ever lose the files or use a new SD card you can just prepare it again.