IMO, do not go ventless! The combustion products (ideally) are carbon dioxide and water vapor, and in central Texas, you don't need to be adding more humidity inside you're home, do you?

A fireplace is the fire box and surround.

The fire box is the box portion of the fireplace where the fire actually burns.

An insert is a stand alone unit that gets placed inside the fire box.

IMO - I always like a fully vented fireplace (rated to burn wood with a gas line plumbed into it). This will give you maximum flexibility to change what products you put into the fireplace anytime you want.

We have a free standing fireplace. With heating oil prices may consider an insert. Any imput would be appreciated, tia.