Everything
@Thebigcheese said is correct. You don't construct a better waveform with more samples. You construct THE EXACT SAME waveform. Any difference at all MUST represent a frequency beyond Nyquist, and that's literally impossible.
The idea of timing being locked to discrete samples is also unintuitively wrong. The examples that are often used to argue that, use samples that "just happen" to line up perfectly with the event in question, and that one snapshot is used for the entire argument. But if you draw the *actual* waveform (not the ideal one), that only has content below Nyquist, and then time-shift *that* by less than one sample while adjusting all of the samples to stay on the waveform, you'll see a less-pretty pattern that still captures THE EXACT SAME THING at fractional samples' difference in time. So you don't need fast sample rates "to get the timing right" either.
(this is one of several reasons why "bit-perfection" is completely unnecessary)
It's also unintuitive, but true, that you can design a series of equally-spaced, finite-valued samples to give an arbitrarily high peak, well beyond the highest possible encoded value. This makes "true peak" meters difficult in digital. You can't just take the highest sample and call that the peak, because the waveform peak is actually higher than that. The vast majority of the time, it's not *much* higher, but it usually is by at least a little bit, and there really is no absolute maximum.
Doubling or quadrupling the sample rate to try and "limit those peaks", as if they were some kind of unwanted artifact...will simply add another sample right on the exact same waveform and not change anything at all. If you were close enough to clipping that the new samples are out of range and can't be encoded accurately, then you've ADDED distortion, not reduced it.
As said before, there are a few cases where it's actually useful to keep a high sample rate all the way through the system. Decoding bat calls, for one example, or non-isolating hearing aids for another. However:
- If you're recording ultrasonics in air (bat calls), then you can't use a normal audio A/D converter, even if it does support high sample rates, for two reasons:
- The analog anti-aliasing filter is still important, and of course doesn't change at all when you choose a different rate. You can make it different from the manufacturer's recommendations, like to increase both the cutoff frequency and the rolloff rate so that it's still sufficiently quiet at the mid-MHz physical sample rate, but of course that's on you now as the electronics designer. If you buy one that's made for audio, it'll start rolling off just above audible, and you can't change that. That's going to affect your ultrasonic recording.
- The digital filter inside the chip, also starts rolling off just above audible, and you can't change that either. That's true even at higher sample rates. The difference is *not* the cutoff frequency, but the rolloff rate above that frequency. So that'll affect your ultrasonic recording too.
- If you need super-low latency (non-isolating hearing aid, without an acoustic comb filter), then *the entire system* needs to shovel samples through fast enough to make that worth the argument. If you use a multitasking operating system (anything that can run OBS), then it's going to fill a buffer while the system does something else, then process that buffer all at once, and play it out at the other end. That completely wipes out any hope of "low latency" on the scale that increasing the sample rate gives you.
- If you're using a dedicated system that does push one sample all the way through before grabbing the next, and you can only afford a handbreadth or so worth of latency compared to the speed of sound in air, THEN a higher sample rate might be useful. Not so much because of the time between samples, but because the digital filter inside the converter chip adds that much latency all by itself, and it reduces at higher rates even when measured in *samples* and not seconds.
(relaxing the rolloff rate, does that)