What matters, the rms or peak value of the Analog signal to choose appropriate ADC for digitization?
An RMS sine wave of 1.3 volts has a peak-to-peak value of 2 x \$\sqrt2\$ x 1.3 volts i.e. 3.677 volts p-p. It is not only that range that has to be accommodated by your ADC but you also need to DC bias the AC signal so that when it is 0 volts AC, the DC level is 3.677 volts / 2 i.e. 1.838 volts.

If you don't do this you will receive a clipped digital version of your input analogue waveform and you may also damage your ADC.

You should also read any prospective ADC data sheet and understand the effects of gain and zero offset errors and take these into account so that you don't get digital clipping.