> Why would you want to use a floating point in between?
Because if you don't you accumulate small errors at each processing step due to rounding. Remember that it is very common for an input to pass through multiple digital filters, EQs, some compressors, a few plugins, then to be grouped and have more plugins applied to the group. You can end up running the sample through hundreds of equations before final output. Small errors at the beginning can be magnified.
Pretty much all pro-level mix engines use 32-bit floating point for all samples internally. This gives you enough precision that there isn't a useful limit to the number of processing steps before accumulated error becomes a problem. By all samples I mean the input comes from a 24-bit ADC and gets converted to 32-bit FP. From that point on all plugins and processes use 32-bit FP. The final output busses convert back to 24-bit and dither to feed the DAC (for higher-end gear the DAC may handle this in hardware).
As for 192 kHz I've never seen or heard a difference. Even 96 kHz seems like overkill. A lot of albums have been recorded at 48 kHz without any problems. As the video explains there is no "missed" audible information if you're sampling at 48 kHz. I know that seems counter-intuitive but the math (and experiments) bear this out.
An inaccurate but intuitive way to think about it is your ear can't register a sound at a given frequency unless it gets enough of the wave which has a certain length in the time domain (by definition). If an impulse is shorter than that then it has a different frequency, again by definition. 1/16th of a 1 kHz wave doesn't actually happen. Even if it did a speaker is a physical moving object and can't respond fast enough to make that happen (speakers can't reproduce square waves either for the same reasons - they'll end up smoothing it out somewhat). Even if it could the air can't transmit 1/16th of a wave - the effect will be a lower-amplutide wave of a different frequency. And again your ear drum can't transmit such an impulse (nor can it transmit a true square wave).
I've done a lot of live audio mixing and a little bit of studio work, including helping a band cut a vinyl album. Fun fact: almost all vinyl is made from CD masters and has been for years. The vinyl acetate (and master) are cut by squashing the crap out of the CD master and applying a lot of EQ to shape the signal (both to prevent the needle from cutting the groove walls too thin), then having the physical medium itself roll off the highs.
The only case where getting a 24-bit/192kHz recording might be worthwhile is if it is pre-mastering. Then it won't be over-compressed and over-EQ'd, but that applies just as well to any master. (For the vinyl we cut I compressed the MP3 version myself from the 24-bit 48 kHz masters so they had the best dynamic range of anything: better than the CD and far better than the Vinyl).