It's very easy to accomplish something very similar to what you are trying to do without resorting to any 3rd-party tools.
In macOS Mojave, the default action for the maximize button is to take an app window full-screen. Notice how the icon displays two triangles facing in diagonally opposite direction.
With an app window is in full-screen mode, the default behavior of macOS is to hide the Menu bar, and reveal it upon hover at the top.
You can press and holding the Option key while clicking on maximize button, to prevent the app window from going into full-screen mode. But this will only maximize the window to reveal all content (which may not necessarily be same as full maximizing).
As this is not what you want, you can achieve a very similar end-result without taking app window full-screen. To accomplish this, simply move the cursor to any of the four corners of the app window, until it turns into a double sided diagonal shaped arrow like one of these (depending on which corner you choose):
Now, with this cursor icon visible, press and hold the Option key, and double click to maximize the app window to cover the entire screen, without hiding the Menu bar (as shown):
To reap the full benefit of this approach (i.e. achieving full-screen mode like appearance with Menu bar visible), it is recommended to enable Dock auto hiding by going to System Preferences → Dock and check Automatically hide and show the Dock.