I wonder if there is a specific logic how shortcuts are assigned. I mean is there a thing like, for global shortcuts use cmd or for app-specific shortcuts use cmd + alt? It looks really random at the first sight, but probably there is a logic I don’t get.
Welcome! Apple’s HIG article is a good read, not too long, and explains some of the principles better than I could. It doesn’t really cover global vs. local shortcuts, but the convention for global is generally to use more modifiers and/or bind to unlikely keys (e.g., launchers use opt+space) to leave simpler shortcuts (cmd+letter, etc.) available for local apps. That reduces collisions.