One thing to watch out for: you're correct on jellybean linear regulators having a PSRR of ~80dB, it is frequency dependent. It is usually good at low frequenci

One thing to watch out for: you're correct on jellybean linear regulators having a PSRR of ~80dB, it is frequency dependent. It is usually good at low frequencies (couple kHz) bu usually falls off as you approach switching frequencies of modern DC-DC solutions (a couple hundred kHz to couple MHz). It is not uncommon to see PSRR of ~20-30dB at 1MHz (e.g. datasheet of L7805 doesn't even show PSRR beyond 100kHz, LM317 is around 20dB at 1MHz). There are linear regulators that are better in this regard though (LT3042 is my favourite for high PSRR).