As for the format, most used format in 3D is usually OBJ Format, which most apps use, not all, but most use obj format.
Since most of the items/objects/products on here are for Poser (not all), OBJ format would be the ideal choice.
This is again my personal OPINION, and AGAIN JUST AN OPINION. For Architectual stuff, I felt Wings3D, 3DS and Cinema4D to be some of the greatest for that type of art/modeling (thou I love Teyon's work, really owesome organic modeling, wish I could do something like that, lol).

Again this is just my OPINION ONLY, and my CHOICE of Modeling for Architecture. I like to create Props/Architecture stuff, and I found those apps said above to be some of the greatest. There are others that say LW is really amazing for architecture as well, as well as Modo, which is my FAV at the moment, besides Wings3D.

So really the same answer as before, try and see. My choice of Architectual Modeling would work fine for say Wings3D, while others may say LW is their choice, thou both our modeling skills go towards Architecture. I try to keep ideas opened and can never say one app is better then another, as that would be a really bad statement.

BTW: Yes I know of the IBM Building, as I am typing this message from it, lol. I work in that building as we speak, and been working here since Winter of '97, which is a few mins from my house, lol, just love it. BTW is now called TREX, no longer IBM...

I hope you find what U lookin for. Again just give it a try to some of the apps and see how they feel for U. Most apps export in formats that can each read properly, except if you going into model posing/rigging and animation, which is a totally differnt area.

Cornelp...