Thank you for your question and I am very sorry about the issue!
I must admit, we have some issues with the connection between ARCHICAD 23 and Rhino 6. Although some of them were addressed with the first update for Grasshopper - ARCHICAD Live Connection add-on, I'm aware that some bugs have not been fixed yet.
To find out which problem you are having, could you take a screenshot of the Grasshopper components used in this case? A video would be even better to demonstrate how slow Rhino is!
Also, you mentioned that there was a crash when opening another window. If this is a crash with ARCHICAD, can you collect the bugID
and share it with me?
Thank you very much!
Technical Support Engineer