Poser 13 as I understand it works very well in Monterey; I wouldn't try to go higher than that if you want a trouble-free experience. If you can, install Monterey on a separate internal or external drive and then put Poser 13 on it. I'm currently using Poser 11 on a High Sierra drive in my 5,1 Mac Pro tower which has a second drive which will have Monterey installed along with Poser 13 -- and possibly Parallels.