What is more important IMHO is to not have the wind flowing across the prop, i.e. not have it at right angles to the aircraft axis. This causes the top blade to see a different wind to the bottom blade, and causes noticeable vibration. Some planes, I gather, have a crosswind limit on their engine tests, for this reason.
I agree. I often do runups not pointing into wind, but make sure the wind is not on the beam.
The runup on the twin star can be done on the taxy....just press and hold two buttons until the test sequence is complete 