Just FYI, setting Barbarians to None at game-start will (AFAIK) also prevent the Goody-Huts from being spawned.
You can easily change the terrain-yields (before and after roads, mines and irrigation) and the existing building-properties using the Editor.
You can rename the existing terrains in the Editor, and if you're a good graphic artist you can also completely redesign them (and several talented artists have already done so). Unfortunately it's not possible to increase the total number of terrain-types beyond the slots already available, BUT some terrains also have "Landmark" variants which can be given different properties (e.g. you could set Plains to be roadable, but LM-Plains to be non-roadable). However, LM terrains can only be added to a prebuilt map, they will not be included in a randomly generated map.
It is possible to add new units, buildings and Wonders to a .biq, but that requires setting up a new mod-folder in
.../Conquests/Scenarios/, and doing additional work with the respective text- and graphic-files, which then need to be saved in that folder.
There are some really good recent tutorials by
@Pelo McSoy in the "Tutorials and Guides" subforum, which describe in detail what you need to do to add new buildings, units and more.