Are you positioning your wrist differently for three fingers than for one to place your fingers at a particular angle on the trackpad? Or just to reach further into the trackpad to make room for the other fingers? If it’s the former, you don’t need to do that, it will work at whatever angle feels comfortable to you.
Most natural to use the track pad is to curl my right hand towards me with my wrist still touching the macbook. One finger feels decent, but already 2 fingers feels a bit off to me. And 3 fingers even worse. It's really stretching my wrist at that point. My wrist is always positioned on right of the trackpad, but putting 3 fingers on the trackpad is putting it at an uncomfortable angle.
Even with one finger I think I have to bring my wrist quite away from the usual position though, off the laptop with its bottom. But three fingers feels uncomfortable even when I do that.