"Pull development" just means shortening the time in developer before dumping chem and pouring in the stop bath. The MDC shows two different times for Tri-X in D-76 1+1, 9.5 min for 35mm and 10.5 for 120 film. It also shows 9.75 min for iso 400. I would be inclined to develope as if it were shot at 400 speed. You have to remember that the MDC times are starting points, and you must experiment to find the time that works for you.
The more I learn about the craft of photography and the better I get at each task the more I like using the box rating.
The results others get are nearly irrelevant because things as simple as their thermometer reading being differently than yours or their metering technique giving different readings than yours (both of which are the norm BTW) or any number of other variables can skew the result.
Shooting any film at half box speed will get you more shadow detail than if you shot it at box speed.
Which is more important to you though, an extra stop of detail or a less blur with a faster shutter speed?
The answer to that question can vary for every shot.
With regard to changing development because of a change in exposure:
That depends on how the SBR of the scene matches the paper your printing on.