Is someone able to merge together the various tri-shapes into one mesh, to drastically reduce polycount?
Simply merging trishapes does not lead to less polys or a significantly smaller mesh size (it will be a little smaller due to a reduction of properties though). To achieve what you want, one would have to delete all invisible/hidden parts of a merged shape by hand to reduce the polycount. It depends on how the merged mesh looks like whether this makes sense or not.