@dimkapenguinYT I've merged your post into this thread as the question has been asked a couple of times now and it's great to keep everything together in an info thread 🙂 I have the iMac with the exact GPU you're looking at and posted above with some tests.
There is no comparison with the 16" MacBook Pro. Even though iMacs are also built using mobile parts rather than proper desktop parts, they have much better and more efficient cooling than MacBook Pros. MacOS throttles power to reduce the risk of overheating so an iMac will benefit over a MBP. Having said that, I also play on a 2017 15' MBP with 4Gb AMD Radeon Pro 555 and the game is fantastic on it (all my graphics settings are always on high).
There are also issues with the game running on the new 16" MBPs which are very specific to those model Macs -
https://answers.ea.com/t5/Technical-Issues-Mac/NEED-INFO-Problems-playing-Sims-4-on-the-16-quot-MacBook-Pro/m-p/8750583#M27203 
