Hi Dan,
Wish I could be more help, but mobile development isn’t my specialty. (I don’t have a touch screen device either.)
The first question I would ask were I in your place would be: do the mouse pressed, released and dragged functions accurately represent touch events on the mobile device? I’m not sure because different flavors of Processing, like Android and p5.js also include a touches array and touch event listeners.
Searching the forum may also provide more information. Two threads which bring up touch are here and here. They both focus on buttons, but may offer some leads.
The next matter I’d think about has more to do with interaction design. How can the user’s touches be converted into a curve animation? For example, a touch started event sets the first anchor point, then a touch end event sets the second anchor point of the curve… Or maybe the distance from the beginning of a touch to the end of a touch can be measured against a maximum possible distance to create a step supplied to bezierPoint and bezierTangent.
Hope that’s a helpful start!