Mt. Whitney (Mt. Vomitorium) Pukers Club Member here (I am so bad I get nauseated looking at Whitney through the Zone's Webcam at sealevel!) so take my advice with a grain of salt.
I find Diamox helpful especially for sleeping at altitude (otherwise awake all night), but it is not anywhere near an altitude sickness (AMS) slam dunk (i.e. you can't pop some Diamox and parachute to the top of Everest and not die from AMS in minutes). For me, altitude plus high level activity with insufficient acclimitization even with Diamox equals tummy AMS.
I myself would stay at Trail Camp as the final summiting camp because 10.5K Outpost camp is 4000 feet below the summit, even Trail Camp is too low at 2500 feet below. But I am a poster boy for "increase altitude no more than 1000 feet per day" official recommendation. Plus, I feel I could more easily get equivalent acclimitization car camping at Horseshoe Meadows (10K) if it is open. Aside: there are some out of the way sites at Trail Camp so it is not all bad but it still sucks compared to Outpost Camp (No trees, No waterfall).
Also, you can book as many days as you want at Trail Camp "Express" even if you don't use them. If I forgot to "book" them, I would still use them anyway. Obviously, late afternoon arrival at Trail Camp and an alpine start means very little acclimitization time! Two nights (arrival and alpine start) at Trail Camp would be the minimum for me without significant off mountain acclimitization. I personally would not leave Trail Camp without feeling pretty good the day before because I would be going up the 99 switchbacks and then miles of hiking at over 14000 feet, i.e. not a quick up/down foray into higher altitude. Super fast hikers/runners can probably get away with it though.
Staying extra nights requires packing extra food because the Portal Store do not "drone" up hot meals and beer. Boo!
