I use the last WW version, and I have none of this issue. I added 5 sims using the gallery in life mode, and have 0 lag. Sims were able to interact normally with each others and objects.
Im pretty sure you have lag because how do you can explain that using the same configuration with 178.3 version and can play with 0 LAG and installing the new one every interaction between townies has to wait at least 3 to 5 secs to responds, and you can see the same problem if you see them interacting between them and not you interacting with them, there is a lag included in the new WW version and im not speaking about playing animations because you can play them ok its just the normal game that its impossible to play. Im sorry but i dont trust you ahaha