I am a PC user and not a Mac user. I have no connection with any product or business mentioned below.
Although all of the X-Plane development work is done on Macs, there is a comment elsewhere in this forum by a Laminar Research staffer (jroberts) who uses a PC to fly. That must be a clue on not using a Mac.
I think the comments in the video you provided a link for has answered your question.
Buy your Mac for work and don't waste your money on anything Mac for Flight simulation. Others in this forum have also made the same comment. Even for a windows based gaming laptop you need to be selective in the brand.
The author of the video mentioned a heat problem. You need adequate cooling for the system. The CPU generates a large amount of heat. So does the the graphics card. The inbuilt graphics component in the Mac motherboard would have generated heat as well. The author makes reference to the graphics cards of today having cooling fans. A must. Otherwise your system will crash (blue screen) and reboot.
For the money you will spend on a mac you can get a higher spec PC. Make sure the PC is 64 bit compliant otherwise XP11 will not run.
A PC will allow you to provide adequate cooling (additional fans) and more importantly you will be able to upgrade your system to the latest components as funds become available. For a better performance go for a Nvidia card rather than a AMD card. The newer top of the range AMD cards may give you the same benefit You should have a dedicated graphics card. The video author touched on this as well. You will also be able to initially use your 23 inch screen provided it is 1920 x 1080 compliant. Any other lower specification will be a disappointment. In time you may want to go for a multiscreen system. This will be far easier to achieve with a PC system.
Take a look at the following youtube video found at https://www.youtube.com/watch?v=j_YQMSeNM-M Take into account the specs for the PC. The author, Michael, runs a company called X-ForcePC producing PCs for flight simulation. His company is the recommended PC supplier by Laminar Research in the USA. Michael has also produced a number of youtube videos providing a number of good hints regarding x-plane.. One additional hint is to use an Intel processor instead of an AMD processor. In other videos he also mentions not using an AMD card.
With Laminar Research recommending a PC supplier instead of a Mac supplier I think answers your original question on what to use for flight simulation.
As a final comment, if you haven't purchased X-plane as yet, make sure you purchase the official version from Laminar Research in either the digital download or disk version. There is a Steam version. This product has been developed by a 3rd party company taking a commercial advantage of the development work carried out by Laminar Research. There is no connection of any type between either party. As a sideline Steam released a disk version of X-plane 11 long before Laminar Research released the official disk version some months later.
Welcome to the world of X-Plane.