Functionally, the process is the exact same as you would do on a computer, but for these, yes, you will need an ADC module. (as the Rpi doesn't have an audio-in built in).

For sanity's sake, I would recommend getting something like a USB audio interface, or a dedicated audio ADC module that contains all the audio stuff (rather than working with a generic ADC and trying to make it work for audio). Something like: https://thepihut.com/products/hifiberry-dac-adc might be a good option to start with, perhaps?

You already have an A-D converter. It's built into every laptop or computer.

Just plug whatever analogue source you've got into the computer's audio input, and you will instantly have a digital version available to you to record or turn into a spectrogram.

Is there an outsized performance bump for this latest generation?

It's hard to forecast what will happen to artistic endeavour in general. Whenever previous technological shifts like this have happened, new artistic roles emerged to utilise the new powers.

But what is certain is that it is going to be extremely disruptive to those who've spent years honing their craft, and are relying on that craft for their livelihood, but aren't superstars. Demand for their artistic skillset is going to go through the floor, and instead it's their meta-knowledge that will make them valuable. But that's a very hard shift to make for many people.