The third level is open to more interpretation. These were often very convoluted and obscure. There was a set of associations around each of the names of the runes. These were presented in the Runic Poems which were a set of verses used to memorize the runes, their names and meanings. It's quite difficult to find good information on this.
Most reputable scholars avoid the topic.
The majority of current writing on the use of runes for magical purposes is done by people who are interested in continuing this practice. They usually have knowledge of other magical systems, and this affe cts their interpretation of runic practices. They are quite willing to fill in the gaps, or reinterpret available information to fit their preconceptions. At worst, they simply make up whatever they think will sell books and new age rune casting sets. Like writing systems, magical systems evolve and change over time.