There are plenty of ways. For what you have, it’s really something that’s easier to make in GIMP than in Blender. But you can change your camera to ortho and enable transparency in properties/render/film and just do a render to make a texture if you want. Once you have a texture, precise application depends on your renderer. In Cycles/nodes, you’d use the texture alpha to mix between a transparency shader and another shader.
Plane doesn’t have to be the same dimensions. Only thing that matters there is a single circle. Tile that across your plane to reduce texture size / improve texture resolution. Render a single circle, make your plane whatever size you want, scale the UV until you have as small of circles as you want.
I’m using the grill mesh as part of the corridor ceiling and may also use it as part of some metal type walkway.
It doesn’t sound like a situation where a lot of Unity devs would have the details be in a mesh. They’d probably be doing it via textures like I’m describing.
No I didn’t have one, but what difference does it make? I quickly did the same thing with the array modifier and the result was the same once applied, I guess it can be quicker?
You can do it anyway you want. It doesn’t matter. Your output is the only thing that matters.
It can be quicker. But what’s more important is that it’s easier to edit. If you want hexagons instead of circles, you do it once, not a hundred times.