Yes, it would be interesting to have another set of data that spans the frequency range 10 Hz to 1MHz to measure 1/f noise. This would require using lower sample rate, about 1 MHz.
The problem with a low sample rate like 1MSa/s is that all the noise above Nyquist (500kHz) will fold back and add to the result. This would severely distort the measurements, since a major part of noise energy would come from that folded back frequency range above 500kHz.
Even with 20MHz bandwidth limit, it would still be 20MHz vs. 500kHz noise bandwidth.
So my suggestion would be to use at least 100MSa/s in order to get a reasonable attenuation of the aliased frequency band by means of the 20MHz bandwidth limit.
How low do we need (or want) to go with such a measurement? For 10Hz, we'd need 10ms/div timebase and at least 10Mpts of data, which we could not handle over this forum. You'd need to provide some server/cloud where we could upload it anyway.