As far as documenting goes, here's my advice. Go for something that will be inspirational to you rather than something that will be a technical documentation of your training. The former will be almost certainly more personally helpful than the latter. If you want to share your training with others, even then inspirational content may be more effective/interesting. Why? Because you're one athlete, that's all. Your training may not translate to something effective for many other athletes, even those with similar goals. That's why it's better if you're going to follow a training blog to follow one a coach is doing over one even a successful athlete is (at the hs level) because you'll get from a coach more varied examples of athletes rather than one single person. However, one person can be very inspirational.
Look up Luke Evans on Instagram. He's a freshman college runner who documented his high school career but mostly with great shots of him running—his Insta seriously looks like a Nike ad, and it's very inspirational.
By all means do keep data on your progress, I'm not saying forgo that as accurate data and feedback is core, but consider any photo/video documentation to be better off as inspirational than documentary unless you're serious about making a film or book or something.