These words are all straight-forward in Chinese:
- 山火 = mountain fire
- 野火 = fire in the fields
- 丛林大火 = jungle fire
- Forest fire = 森林大火, or 林火
- Forest fire on a mountain (explicit) = 山林大火
Note 丛林 means jungle/bush; Forest in general is translated into 森林; 野 in 野火 means 田野(field) rather than 狂野(out of control), but even many native speakers misunderstood.
So to answer your question,
- 山火 is not a generic word for out-of-control fire. It means mountain fire.
- 野火 means fire in the fields. It sounds a little less formal than the other words but still fine to use. News broadcaster may choose long form 田野大火 or 山野大火。
- 丛林大火 means jungle fire.
- When you want to say 'fires in a forest on a mountain', any of the following is fine: 山火，林火，森林大火，山林大火。