Thanks iternabe, this is really helpful. I've been muddling through recording basics and have happened upon the mostly the same conclusions you have, but have still learned a lot from your thread here!
One thing I've noticed, is that indeed you audacity "good level" graph is how the theoretical ideal appears - something similar to the "average around -12db, with true peak at -6db." But when I output that, it's still tends to be on the very quiet side, especially compared to other recordings found online. The only way I've found to really fix it is to use a limiter to drop the peaks way down, and normalize closer to -3db or -1db, and honestly, it really starts looking like your "too loud" graph when it is finally comparable. I'm wondering if it's because of something I'm missing, or maybe I'm just used to the "git louder" culture of scream-casting...