Hi,
Well, I’m afraid, that there are still several limitations while using the IPR mode because 3ds Max isn’t primarily designed for it and a series of cheats are being used (from the renderer side and from our side) to make it work.
If you want to use the Points Cloud viewport mode while adjusting items in the Custom Edit mode, you can “reselect” the Style - Small Dot / Large Dot mode to “refresh” the viewport.
We'll check what can be done in future versions, but unfortunately, it’s really hard and sometimes even impossible to fix issues that occur with the Interactive Rendering (because of reasons mentioned above). Thanks for your comprehension.
Best regards,