as long as you're sticking to a budget then all is good.
not sure if you've thought about doing stuff in a slightly different method to help save some tris. you can keep the shape in your arches by turning them into a cap that covers a low poly plane behind it. below is a pic of what I mean. At the mo i think you're true meshing everything in, which is completely valid, but if it's costing you lots of tris to do that then it becomes quite inefficient.
making your arches like above means you can save tris, but keep a smooth curve. just a little trick that might help
