Beginner questions

Not sure why you've created a bus, but the default stereo input setting has nothing to do with panning. What you can pan depends entirely upon what sort of session you've chosen. It needs to be a stereo session if you want stereo panning available. In a mono session you don't get the option. If you put mono tracks into a stereo session, then you can pan them across the stereo field; if you put stereo tracks into a stereo session, you get a balance control instead, which doesn't do quite the same thing, simply because you have two slightly different channels if it's proper stereo. If you have pan controls but can't hear any effect from them, then there's a chance that the Master channel (which is where you need tracks to be routed to) may have its mono button selected. It's just above the 'Read' tab in the mixer and shouldn't be glowing green.

To view both the Editor and Mixer at the same time on the same screen, you have to pick up the mixer panel by it's name and drag it around by the mouse. Everywhere you can move it to will glow purple when the mouse is over it. If you let go the mouse on one of those, that's where it will re-dock. You can also undock it completely and have it freestanding if you want, and you can do all of this with any panel. You can even shove it off onto another screen if you have one. Once you've got a layout you are happy with, click on the three little lines beside the word 'Default' at the top of the main display and save your layout to a new workspace. It will then be listed along the top, and you can select it whenever you want it.

Can't tell you anything about 96k on Macbooks, because I don't have one. Neither do I ever find it necessary to work at 96k, because human hearing in adults effectively cuts off, even if you have good hearing, below 20kHz, and either 44.1k or 48k (the audio standard for video) will cope with that just fine - the sample frequency has to be twice the highest audio frequency to avoid Nyquist sampling issues. If you work at 96k, you use up twice as much storage for everything, and you are using up more resources in your computer - which can be a real issue if you start to add heavy-duty effects. And absolutely nobody can tell the difference afterwards - that's all been carefully researched. Anyway, just sayin'...