I am fortunate to have trained as a Dharma Worker at a Zen Buddhist Temple while pursuing a PhD in neuroscience. Congrats on entering the vast worlds of meditation and neuroscience! Your ideas about how meditation affects the brain are pretty good (cells that fire together wire together, at least in Hebbian plasticity), but they could be supplemented by an explanation of the default mode network (DMN), which is a big circuit in the brain that it active when a person is focused on nothing in particular. After all, meditating affects the meditators beyond the time they spend meditating. It improves their attention in general because meditators are better able to suppress their DMN as they shift to a task-positive network (TPN, a big circuit in the brain that is active when a person is performing a certain task) while they are engaged in activities that require focus. The ideas could further be strengthened if you detail the TPN of people engaged in different kinds of meditation or different mindfulness exercises.

Wishing your the best in deepening your meditation practice and understanding the black box between our ears!