The footage from other YouTubers like Vaati was only a few selected missions from Chapter 1 and this shows the same missions so spoilers should be extremely minimal. Your AC will probably be very different too depending on what you build so in my opinion it'll be pretty safe if you're okay with a few missions in Chapter 1 being spoiled. The end of the video has the final boss of Chapter 1 so you could stop at 11 minutes in to avoid that but even then AC isn't like Souls at all so spoilery stuff is way less damaging to the experience in my opinion.