I'm in the exact same situation - we'll be taking wife's Y on a long road trip. I agree with above - I use FSD in my M3 on highway all the time and it is an absolute game changer. In addition to the above, the absolute killer feature is the ability to be in full TACC (or FSD or whatever), and you decide you don't want to wait for the car to figure out it should change lanes (it will in full FSD and it's good but I'm impatient too). Without FSD/EAP you must "break" TACC to change lanes, then reset it. With FSD, you simply partially engage the blinker in your desired direction, and the car then gracefully checks for obstacles, and obligingly moves into your desired lane -- while all this is elegantly displayed on the nav screen. No need to break or reset anything, and if you missed someone in a blind spot - the car picks it up displays the vehicle in red and waits until it's clear, then executes. (You didn't comment on whether you purchased EAP so I'm assuming you did not. In a 2023 M3 you will not have hardware concerns.)
The suite of features IMO dramatically reduces stress and fatigue that come with highway driving.
To see exactly what comes with the package,
in the car bring up the menu (tap the car) then go to Upgrades and select the FSD option -- it lists in bullet form specifically what's included.
Of course, whether something is "worth" $200 ultimately is a subjective thing. Enjoy the tip!