Quads are prefered as they can be easily subdivided and they smooth better too, So in this case he should be ok.
Triangles are not really a problem in poser and DS espicially if they are on flatish surfaces of a ridgid objects, (like this chaple).
Ive even bought some clothing items on the Daz store that were ALL in triangles, and they render just fine.
Its N-gons you really have to watch out for as they wont render correctly in either program and are considered bad topology in general.
Very good model, the only thing I can see that is any real cause for concern is where you have cut a hole for that round window, it looks like you made a boolean cut, becareful with those - as they leave quite a mess behind, but since the cutting surface is flat you might get away with it on this particular occasion
Normally I would cut an approx hole manually, it doesnt have to be as circular as the actual window either, it could be little more than an octogan, since that curved window frame/border (where you used a tube primative) will cover up the 'approximate' hole nicley. Doing it this way you aren't left with a bunch of irregular topology, which may or may not render well on the exported mesh.
One other thing to bear in mind, Poser and DS will discard any smoothing group information in an .OBJ (exported format), for this reason, you might find you will need to break the verts that make up all your sharp edges and corners or preferabley, bevel/chamfer them, otherwise DS/poser might try to smooth over them (not a good look) you will want to retain those nice clean well defined edges.
i would do a quick test export/import to poser now to check out how it renders in its current state.
Those areas where you have chamfered edges should be just fine though
Thats the golden rule for a mesh intended for DS/Poser, if you want a good clean edge, you must either; chamfer, bevel or break verts.
breaking verts should really be avoided if you intend to use a displacment map though, or else you end up with broken seams, (gaps)
You texture work is looking really nice
If you dont end up needing to break verts on edges I would definately suggest you add a displacment map for the masonry and it will look amazing.
If you have only been doing 3d for a few months, you are doing very well indeed. Nice work.