Gotcha. 

You can export any model from DS in obj format and it will load in Poser. The export menu has an option to export it in Poser scale. It's not always correct but it's usually close enough to work with. You can scale it down further if needed to get it to the size you want it then export and re-import in Poser and that bakes in the Poser size you want.

For A and T pose clothing conversion, you can pose the clothing in DS and export it in that pose as an obj. It won't have it's rigging but you'll need to re-rig it in Poser anyway for it to work with whichever figure you want it to fit. You'll need to use a combination of the morph brush and magnets to really get the clothing model to fit the figure you want it to fit. Fitting room can do an alright job with some things but that's an algorithm that's more or less just pushing the clothing geometry to the figure geometry and doesn't allow much control like morphs and magnets can. Converting clothing is one of the tutorial ideas I've been working out for when I release my figures (yeah that's still happening), just haven't gotten to it yet.