Can Demon Slayers use multiple breathing techniques like fire and water or are demon slayer corps all capable of just 1? Also is the ability to use certain techniques passed on by the parents through genetics or does it just depend on what the Demon Slayer learned first?
It is shown that Tanjiro can use the water and the 'fire god' style, which probably is the original sun style. In the same figth Tanjiro says that it is hard to switch from one breath to another, so the styles may be somewhat incompatible.
For the same reason, it seems that other slayers use only one style because of their deep specialization, and not because they cannot learn another one, as it is a physical skill, not a passed supernatural ability. Later in the story Tanjiro explains how to push oneself to use the marks, so the styles are transferable in some sense.