I guess I’m even more confused now
but thanks for all your answers!
The simple idea:
Almost all DACs are delta sigma, and oversampling(much higher than 96 or 192kHz) is necessary as part of the design. To oversimplify, so the main concept is clear, imagine the DAC takes the digital signal and turns it into 1 and zeros but with a different code where 1 means the voltage goes up and 0 goes down. No fixed voltage value, just the given direction of something changing constantly. With very many samples per seconds, and the speed for amplitude increase/decrease being very high, the amplitude movements outside the original signal can only contain very high frequencies. It's crap noise created by that apparently crude process, but because its content is made of very high frequencies, we can just low pass the high frequencies somewhere after the music content and have excellent attenuation of that noise. Leaving us with very high fidelity.
That's the general principle and why we want oversampling, it helps keep music and crap easy to separate and at a lower cost.
In reality, it's more complicated, because true 1bit DACs are a mistake(same as to why DSD is a mistake), so almost all DACs nowadays work with a handful of effective bits?
Also, some of the oversampling(upsampling) in the DAC is done as part of a reclocking/anti jitter process. And really, in modern DAC chips, some more DSPs can be involved for various reasons and those tend to run better at a particular sample rate, which is another reason to change the sample rate as needed where it's needed.
That's for almost all DACs.
But of course, elite audiophiles won't settle for what the plebs is using(even when it's the best solution...). So you will find some true one bit DACs for a DSD playback that's as bad as the early days of DSD players, and it might also convert PCM so the signal can enjoy 1bit problems too. It turns out fine because luckily with DACs, even bad stuff tend to sound nice and measures better than the rest of the playback chain.
And of course, You can find a few R2R DACs. Some are non oversampling(NOS), which is objectively also a mistake from the old days. And that's where the genius of selling solutions to problems we created ourselves, comes into play. You can get a nice software for your computer to use the fanciest oversampling before sending the signal to a NOS DAC you probably paid more so it does less. It's a beautiful world.
I'm overly sarcastic, and I oversimplify, but it should still be mostly right.
