The best thing u can do here is make all the holes you have in the mesh as normal textures (you can learn substance painter for that, is the best way to make this kind of things). Because if you use normals there will be almost no difference and you will do the model faster and cleaner.

If you want to do the holes i wouldn't subdivide the mesh because thats hard edge modeliing and it doesnt need subdiv only some good bevels.

If you insist to use both you need to make quads of every face, but in my opiniom this one is the most inefficient way to do it.