Hi, I have created a grate similar to the one in the photo, but with some asymmetry. I was wondering if anyone had done something like this and have some tips on making the Booleans faster and making the finale result less geometry dense.

I would not use booleans for this, there's a much faster way. You can create it in 2D first, i.e. you duplicate a bunch of circles and put a rectangle around them. Make sure that the circles and the rectangle all lie on the same plane, for example all on Y position 0.

Merge all of these 2D geometries together and follow up with a Hole SOP to generate the polygon with holes in it. Then you can extrude the polygon.

Another option might be to use a shader with an opacity texture instead of doing it as full geometry.