I need to upgrade my MacBook Pro for gaming

Welcome!

I've used X-Plane for Mac in the past and even older versions were very demanding of resources and liked high-end video/graphics hardware.

The biggest limitation IMHO for any flight sim on a MacBook Pro is the heat production. X-Plane used to run up the temps quite high on my old iMac that had three fairly large fans. My current iMac 27 5K has one fan and less interior volume, and the v11 demo ran quite hot on it.

Notebook computers simply cannot have the cooling capacity of a desktop. The 13-inch model have but one small fan; the larger models have two, still small. Our family lost two older MacBook Pros due to hear issues so I'm a bit snake-shy about stepping in that again.

The Apple desktop options are not much better. Current skinny iMacs have little more cooling ability than Macbook Pros. The only one that looks capable plus has more room to move air is a Mac Studio. They start at US$2000 but you get 32GB RAM with that config.

https://www.x-plane.com/kb/x-plane-12-system-requirements/

👉🏻 However...

There are few simmers here. I think you will be far better served by reviewing X-Plane's Knowledge Base (https://www.x-plane.com/kb/) or the X-Plane section of the forums at AvSim (https://www.avsim.com/forums/). I beta-tested a sim years back and the heavy-hitters for simming hardware questions could always be found on AvSim.

You are not going to get a lot of responders with Sim experience here. Even my knowledge is rusty now.

PS: My qualifications once included, "I wore out a joystick."

For XPlane I would go with the 32GB of RAM. If you look at the Recommended Specifications for XPlane it mentions 16G-24G of RAM. Most games don't take huge advantage of multiple CPU cores. Since the specifications only mention 4+ cores I don't think CPU cores will be as important or they would be clearly stated. The lowest end AMD CPU listed under Recommended Specifications is the Ryzen 5 3500 which has just 6 cores.

Disclaimer: I've never played XPlane (may have tried the demo years ago).

Honestly, I don't think it matters that much. Buy the most power you can afford with the highest amount pf RAM you can afford and play on.