Since Archimatix is a non-destructive modeler that gives you great control over detail level, you can iteratively reach the optimal triangle efficiency versus aesthetic richness you would like for your model by simply dragging local parameters in the nodes or the global Detail Level slider.

Triangle density tends to be a product of 2D Shape segmentation.  You can set the segmentation of Plan and Section shapes to control the number of triangles in the meshes generated by the shapes. As you model, if you think certain forms look too faceted, you can go to their generating shapes and up the segs parameter.

Alternatively, you can use the Detail Level parameter at the lower right hand corner of the Node Graph Editor to decimate segs variables where ever they are found in the graph.

You can also use this detail control to create LOD version of the model. Eventually Archimatix will have an LODGroup creator.