Using a stopwatch isn't accurate at all, but depending on the app, might be. Even trying to watch a video and use a stopwatch, or time stamps won't be that accurate. Speedo and tach usually have some delay to them.
I have also verified, with multiple runs, probably more than anyone else in this forum, that using 4-high gets the best launches without worry of wheel spin. Using 4-auto is slower due to power loss through clutches in transfer case. If you can prevent wheel spin, 2wd should be the fastest, but it's touchy getting a good launch without wheel spin.
When I run at drag strip, if only doing 1/8 mile, I stay in 4-high the whole run. If running 1/4 mile, I will switch from 4-high to 2wd after shift into 2nd. I will still get some wheel spin on 1-2 shift at WOT in 2wd. Switching to 2wd on 1/4 mile runs dropped 1/10 of my times.