Camera 3D Orbit with Mouse Input in Unity - Proper and Simple Way

I repeated exactly the same, but for some reason it works very well up and down for me, but it is extremely naughty when rotating horizontally, why?

instead of needing to hold a button, can you make it so that it just moves with the mouse from the start(no button press)?

Been trying to add this to my camera script but to keep it from drifting and only orbiting if holding down middle mouse. Unfortunately it conflicts with the camera script I already made. Plus its huge as is.

Thanks for the video! I'm super new to C# and Unity so these types of quick tutorials are great for experimenting. I'm getting an error however. Invalid expression term '||'. Any suggestions on how to address it?