I don't have the powertap wheels but I'm familiar with the DT R460 rim - I've run 700x23 tyres on mine without issue, and most people don't tend to go smaller than that nowadays?
I'm also interested in these wheels. I have a G3 hub on another set and agree it is a solid and reliable power meter.
Can anyone say how wide the rims are? I have an old Six13 frame that doesn't take wide tyres - eg I can't run 25mm tyres with Archetypes rims as they are too wide. 23mm tyres are fine. Are the R460s particularly wide or not?