You might be thinking of A9LH installations without OTP, which I believe turned out to be dangerous and problematic (must have been, it was removed from Plailect's guide). This was New3DS only.
Depends on the guide, honestly. The reason people, including myself, recommend 3ds.guide is because it has been proven to work, time and time again, which has garnered trust from people. Video guides aren't necessarily more dangerous (they can be, of course), but they haven't been proven anything like 3ds.guide has. Just be wary when following the instructions, and make sure to use your own OTP. The fact that you're following along with 3ds.guide is even better. So, you should be fine.
Note that the written and video guide probably differ at certain points; if you notice this, side with the written guide, as a general rule of thumb.