Two-finger scrolling on the K400+ is painful. (Actually physically painful; I have RSI in my right arm and poorly-tracking touchpads can be a trigger.) It requires fairly heavy pressure on the touchpad to trigger gestures consistently (though they can be triggered inconsistently with light pressure which is also frustrating). And especially on macOS, it's difficult to actually scroll a consistent distance with a two-finger gesture with the K400+.
I'm fairly certain this has to do with the K400+'s touchpad not being recognized as a touchpad by the OS. The device is instead emitting mouse wheel events in firmware when a two-finger scroll gesture is detected. macOS will then, of course, apply mouse wheel acceleration, which makes sense for some mice but absolutely does not make sense for a touchpad.
In fact, I think I like the trackpad on my cheap Logitech K400 just as much as the Macbook, I'd be hard pressed to point to a significant problem with either.