Is the peak-to-peak voltage the same as the peak voltage in rectified voltage?
You can use the formula:
$$V_{\text{rms}}=V_{\text{peak}} / \sqrt{2}$$
for:

pure sine waves (with zero mean)

fully rectified 1., with ideal diodes




Image adapted from: https://en.wikipedia.org/wiki/Rectifier

The other formula is just a consequence of:
$$V_{\text{peak}}= V_{\text{peak-to-peak}} / 2$$
for any waveform with symmetrical min. and max. values.