If you want to stay in the realm of aligned content then this is pretty much it. You got a matrix/array and somehow fill it with values.

Doing continuous content generation is pretty much more complex and I'm not even sure it buys much, many games naturally fit in a "tiled" world.

For a start however, I'd consider the idea of not using BYTE, but rather use a more involved data type allowing for more modification.

How are you using those numbers right now?

I hope you're not doing things like:

if(level[idx] == 1) {
  DrawFloorTile(...);
}

so you could elaborate on the meanings of those numbers. I do something similar myself with pooling resources, in your context it would look like

for each tile
  const size_t tileIndex(level[idx].loadingIndex); // checked for validity once at load
  Tile *uniqueModel = loadedTiles[tileIndex]->model;
  DrawTile(model, GetWorldPosition(idx));
}

This allows you to move to a more data-oriented design were you don't need to keep magic numbers in mind.

But maybe you're asking for something entirely different? Please elaborate on your concerns!

As to not get to far off track from my original question, why is the data oriented design better then the
first code example. I'm not questioning it's actual purpose or efficiency. I have just heard the name "data oriented design" before
and would like to know what that is. You don't have to give me a full blown explanation tailored to me. I take links

It's more or less like equations, where we write x + 7 instead of two numbers. This does not come easily as we have to write stuff that adapts to every (meaningful!) configuration for us, thinking in advice what we need. Of course if I tell you what amounts to x + 7 you cannot give me an answer and similarly in code we cannot get a solution... but we have to write code which somehow outputs the correct solution for us every time. We do that by exploiting properties the data is guaranteed to have and to define those properties we need to define the problem.

So for example in a tiled world we might be interested in knowing, for each cell in the world (not each tile):

1. how it look?
2. is it passable?
3. if passable, sound of footsteps
4. if passable, deals damage?

So we might want for example to make a specific cell passable even though it typically isn't, because that's a classic for hiding secret goodies: going through a nonsolid wall. In general we have to decide which property is part of the world cell and which is part of the tile itself.

Instead of defining properties in code we define them in the data itself.

Let's assume for easy explanation we load each tile graphics from a file. Then the actual tile graphics data is not really relevant: we just have to load it up completely, pack it in a texture and draw a quad measuring - say - 2x2 world units.

But now I'd stop there and let you figure out what you need to pack in your world.