The only icon that cannot be tampered with is the Notification Center. Want to place the Setapp icon over to the area of the bar once reserved for first-party apps? Do it!
Don’t like the clock all the way over there on the right-hand side? Drag it to somewhere more suitable. There are no restrictions here - feel free to move icons anywhere you see fit.
To move an icon in the menu bar, hold Command (cmd), then click and hold the icon to drag it across the bar. And if you are not there yet, it’s time to upgrade to the newest macOS anyway. The users of macOS Sierra and later definitely have more creative license here than others. How much freedom you have to rearrange items in menu bar depends on which version of macOS you’re running. Try free ✕ How to rearrange items in menu bar
