[whpalmer4]

I find that it leads to lots of spurious mouse clicks, so I don't use it. If it works for you, that's all that matters — but I'm not testing my suggestions with that setting.

I turned on One Finger Tap to Click and Dragging on both iMac (with MT) and MacBook Air and found it to work exactly as expected at all zoom levels, with the caveat that it is very easy to get an extra tap in there, which results in selecting the text. If your finger lifts on the second touch, that gets treated as a double click and you get the undesired text selection. I don't see any evidence that it behaves differently on different hardware, except to the degree that the sensitivity of the hardware to those accidental touches may differ. If I make sure to stick my finger on the second tap, it is 100% reliable. Of course, it is with the trackpad button, too, with no special care needed, and some days the trackpad button represents the bulk of my daily exercise :-)