MacOS FAQ and troubleshooting

Some users experienced trouble running RPG Maker games on their Macs so I decided to look deeper into the problem and make a how-to guide. These problems are not present on all systems and depend on the local security configuration.
1. Download the game and navigate inside the folder to find the Game.app
2. Choose "Get Info" from the context menu and scroll down to the Sharing and Permissions part.
3. Check that your active user (marked with (me) after the username) has Read and Write permission.
4. If it's not the case - set it yourself via the menu. After changing permissions click on the gear icon and choose the "Apply to enclosed items" option from the drop-down menu.
5. Now we are sure that your access rights are adequate and that you are ready to add the game to your applications. Do so by drag-and-dropping the Game.app into your Applications directory (by default it’s displayed on the left side of the Finder.) This will require Administrator access.
6. Run the game and get inside the options right from the main menu. The first time you execute it MacOS will warn you that I am not a licensed Mac developer. Oh noes. Ignore it.
7. Change something like a volume level in the options menu and hit escape to check if the error appeared on the screen.
8. Start a new game and try to save your progress. Check if you can save the game and load it afterward.
9. Great! Now you can be sure everything runs smoothly.
If you can't launch the game by just clicking the game.app icon, try to opening the content folder, and using the NWJS terminal icon within the MacOS folder. 
Alternative solution
Thanks to BlazeKiin, we have an alternative if the original method doesn't work in your case. You can read it in full detail here - https://pastebin.com/U5gV8sW1
The short version sums up to: "The two main parts is after you open a terminal, you copy-paste "sudo  xattr -r -d com.apple.quarantine " (with the space at the end) then drag and drop the game, click enter, and type in the password.
Afterward, you click on the "show package contents" and then into "Macos" and  type in "chmod +x " into the terminal and drag and drop the one file in "Macos"
How do I transfer my progress from an older version of the game into a new one?
Normally, you just copy your entire save folder from the old release into the new version of the game. By default, the save folder is in the www folder of the game. That’s it. But MacOS is different from other  platforms and keeps the save folder on a different path inside the game  client, namely - MGS_080_MacOS\Game.app\Contents\Resources\app.nw
Thing is, MacOS treats .app as executable files, so you will need a file manager to open it up as a folder and look inside.