I'm not a person – I'm a ghost, or even a lich!)))
In my opinion, Heroes 5 needs catchy names, but the name for the fire race sounds as unappealing as it did in the third game.
So, what's the point of giving the lizardmen an explosion ability if they shoot?
Will fire elementals then remain neutral? Are we going to discard all sorts of weak creatures?
A spirit turns into some weak mage, level 1, with only 3 mana.
Regarding the entities – let's assume they cast spells and let's assume they have a ghostly appearance (although a ghostly appearance is only characteristic of necromancers), but they still turn out to be too strong.
In general, I think that one could only consider such a race before the expansion with the dwarves was released. Without fire dragons, they look weak, even with a phoenix – it just doesn't feel right.
The lizardmen shoot with mana, and only the upgraded ones do.
Fire elementals and phoenixes will remain neutral, but will become part of a specific Faction.
The spirit only casts invisibility for itself.
Let the entities be weak and have low initiative.
And the young fire dragons at level 3 can really be replaced with something...
If you have more questions, write...
Added 1 minute ago
And about the race, I said – if necessary, change it – you'll be the... co-creator or something like that...