Hey, I've been playing around with Poser 11.3.818 and I'm disappointed to see that the viewport still has a lot of the same problems as older Poser versions. Whenever I had more than a few figures present the framerate starts to dip, and with larger scenes it gets down to what seems like the single digits, or at most low double digits. This is with all of the preview window settings set to the lowest possible value; I experimented with the preview settings. I use Texture Shading, although none of the other shading options seemed to help the framerate either.

Some of the scenes I'm dealing with are pretty big, but in my experience other programs like Blender and DAZ can handle bigger scenes with better framerates, so I'm frustrated to see Poser becoming nigh-unusable under the same conditions. The framerate gets even worse when moving figures in these scenes; I know about the fast/box viewport tracking options, but they make it hard to see what's going on at best, and at worst, glitches make those modes totally unusable in some scenes. I'm using a machine that's far more powerful than the recommended Poser specs, so it's frustrating that viewport performance seems only marginally better than when I first played around with the program on a much weaker system almost a decade ago.

The closest thing I could find to a "fix" on the forums seems to be just making objects invisible when I'm not moving them... which is a pretty major annoyance in and of itself.

One other issue, which is admittedly less important: fairly often, when I'm rotating a camera around a figure, the camera suddenly flips upside down for no apparent reasons. It'll go back if I keep moving the camera, but it's a very jarring and annoying glitch that's persisted through multiple iterations of the program, so I'm surprised it hasn't been fixed.

I don't want to be negative, because there's a lot that I like about the program, but it makes it very frustrating to use Poser in larger scenes! Is there some trick or fix I'm not using? Or is Poser just really slow when dealing with larger scenes?

I know you said you're using better than poser's recommended specs, but I wonder if they had crowd scenes in mind when they wrote those. I used to have problems with even a few figures in a scene until I updated my video card. It's still not that great so If I get a crowd, I have issues. My suggestion is to turn off the texture shading and setting everything to a minimum while you're setting up the scene and only turn them up when you want to render.

https://www.renderosity.com/rr/mod/tutorial/?tutorial_id=3044&page_number=9

That's the setting I use while setting up large scenes. It looks terrible, but I can work with more figures that way. Also, if you don't want to hide figures, try hiding just the hair. Both higher poly trans mapped and strand hair will slow down the view port.