No all clothing is appropriate for conversion. If the mesh is not one piece, or if it has a lot of decoration like grommets or ties or laces, it may not sim well.

The way I determine if it's worth trying is importing the obj file into Blender. Wings3D or Silo or whatever you have would do as well. I spin it around in all views: if it looks like it's in parts, then I move on to something else.

If you've brought an obj (File -> Import -> Wavefront obj) into Poser and during the sim the thing appears to fall apart, chances are it's not contiguous.

That's just step one: deciding.

If it is indeed suitable, you'll want to parent it to the figure it's going to be simmed against. Then, for like strappy dresses, you'll want to make the straps constrained to the figure so they don't fall off the shoulders during the sim. I do my grouping in Blender because Poser's interface for grouping is so much clunkier and unreliable.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks