I'm one of the many newcomers to FSD on 10.8. All is well so far, but I wanted to ask some questions that hopefully others already know on what to expect in certain scenarios. I can go out and test this stuff if others don't know, but hopefully I can save myself some time here. For clarity, I have FSD and options already marked in my settings. I've successfully tried FSD by having a destination, double-tapping stalk, and pressing NoA button and I successfully made it to my destination.
it's easy to get confused, as you are seeing the car in transition from one software stack to another. The simplest way is to break apart driving into "freeways" and "non-freeways".
When you are on a freeway, you are using the older, non-FSD beta stack. You will notice in the cars-eye view (road visualization) that all the color disappears, you just have a plain gray view of lanes, and you are back to using "good old" AP/TACC/NoA. The FSD stack is dormant, and the car behaves just like any non-FSD car, doing lane changes etc according to your normal non-FSD beta AP preferences (including turning NoA on or off).
On non-freeways (basically everywhere else), the FSD beta stack will take over, and you will see the colored cars-eye view (red lines for road edges etc). This is where the full FSD stack is running, and the car will (or, more correctly, will attempt to), drive on city and non-freeway roads.
The car will move seamlessly between these stacks to follow a programmed navigation route, and you can see it switch back and forward as the cars-eye view changes. So if you engage NoA on a freeway, the car will switch to FSD beta as you move from the freeway to city streets, and vice versa.
Occasionally, if you have really bad weather, the car may decide it is unsafe to use FSD beta on city streets. In this case, the "color" cars-eye view will vanish (even on non-freeways), and you will revert to the old non FSD-beta TACC behavior until conditions improve. You can also revert to this manually by disabling FSD beta in the Autopilot control panel.
At some point Tesla will retire the older AP/TACC/NoA stack and switch to using the new FSD beta stack for ALL automous driving, regardless of the road .. this is the so-called "V11" version of FSD (not to be confused with the recently released V11 software, just to add to the confusion).