While I typically dislike the practice of basing characters personalities off of their elemental affinity (magical or otherwise), it does make for an interesting creative drawing exercise. Especially if you decide to go that much deeper in personality.
Its very common to make the earth-type character stoic, slow to anger and steadfast in beliefs and virtues. Lots of work needs to go into making this kind of character not boring, especially in terms of powers or abilities. Theoretically it would take a large amount of power to cause earthquakes or pull giant structures from the ground, and also its hardly very subtle to be operating in a city leaving unstable buildings, large walls and craters in your wake.
So I tried to focus on parts of the earth element that wasn't just rocks and earthquakes, more granular mineral types like sand or malleable like clay. This makes for a finer control of abilities needed, and a more adjustable mindset when it comes to problem solving.
Obviously common defensive techniques would dominate the characters arsenal but by the same token I've given him room to use different strategies and the ability to operate strongly in an urban area where you might not always be standing in a place where you can easily gather a large amount of dirt or rocks.
Fire element characters have a pretty obvious character embodiment already, brash, quick to anger and destructive, but fire also has a lot of non-villainous qualities too. Being very fast acting could make all the difference in decision making and in combat especially can give you the upper edge.
In fights, fire is typically shown as the common or basic element widely used for its easy level of power, but in the real world, fire has very little physical presence, meaning that you'd need to reply on constant, speedy attacks and streams of fire to stay in the fight. Fireballs and flamethrower attacks wouldn't necessarily have the knockback and versatility as in movies and games.
Thats why I instead envisaged a more fast paced, skillful fighting style for Calor, matching fires quick movement and overpowering growth.
I figured one of the key features of wind was its momentum and unstoppable relentlessness, so while Anemni might not be quick and skillful like Calor, she uses built up speed and motion to her advantage. Again like fire, air or wind has little physical presence outside of when there is a vast amount of power behind it. So I see air-type characters using wind in a more motion based way, more powering themselves than slicing through enemies with wind-blades. Not to say that direct attacks would not be effective, but I think using winds more natural attributes primarily in a fighting style would be easier to wrangle into a more long term stratagem.
Water users are pretty much always shown as the healers in media, or at the very least using their powers in a primarily beneficial way. I like that water has many different forms and can fit a very large number of roles, from water blasting and steam scalding to ice-shaping and vision clouding mists.
As a result, Marridew fancies himself more a rogue kind of person, staying in the shadows, using his wits to find information and small bursts of his abilities only where they will provide the most benefit.
All in all, I think I managed to strike the right balance between typical portrayals of elemental character types and thinking deeper on their element's attributes and behaviours.
I really have no plans for these characters other than the idea of them in a Deus-Ex or other character-action-RPG setting fighting lots of bad guys and solving mysteries.