Which Poser version? The OpenGL preview is improved in each version, and PP2014 (dunno about P10) also has a Firefly preview window for checking out something like light and other effects. A bit slow, but faster than a render.

You can check any shadow mapped light with its shadow cam. but AFAIK, that won't work for raytraced lights. Still, it can be used before switching the light to raytraced I guess. And IMO one should always use raytraced shadows. They just look better.

(one exception might be animation where using shadow maps ought to give a faster render)

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.