I done only very few subjective tests with MixPre vs MixPre 3 II (mostly tested line-in) before send back MixPre 3 II to reseller for replacement due hardware factory defect in line/headphones-out. But here are my secondary impressions:
First i tested MixPre connected to Edirol R09HR line in and compare MixPre 3 II.
And next i tested MixPre 3 II preamps.
Old MixPre with its analog limiters can produce very pleasant "warm" "well compressed" sound without any additional adjustment. Its low cut filter looks different when you start to look at sound spectre image. It still need come compressor/saturator to slightly boost sound, because 24 bit recordings are usually recorded at low levels to avoid clipping.
Old MixPre use stepless analog pots, and so you can adjust volume in real time very smoothly if needed.
Overall MixPre+R09HR (based on Wolfson WM8786 A/D chip) is actually holds very well. In high frequencies range R09HR line-in appears slightly less noisier than MixPre-3II line-in. But that difference is tiny and only visible if in post boost ultra quiet levels to extreme +24db.
Probably more noise in high frequency is the payment for wide dynamic range multiple combined A/D converters design. (but i really need to redo those tests again with new unit)
MixPre 3 II is sort of more perfect digital clinical and transparent sounding. Its limiters are probably some sort of FPGA VST limiter plugin working in clipless 32 bit mode internally. Its low cut filters are very precise and simple when you start to look at sound spectre image. But it is sounds better than Zoom preamps for sure. It is kind of RAW recorder for audio and is up to your skills to shape final "look" in post. You probably need to experiment really a lot with different limiters plugins and compression effects to produce less clinical sound and shape high dynamic range audio source to something that pleasant to ears. Something like “Limiter №6” all-in-one solution may help a lot
https://vladgsound.wordpress.com/plugins/MixPre 3 II use digital controlled pots with fixed digital hard steps, and so if for some reason you adjust volume in real time you may expect some stepping effect. So it is better do pan and volume adjustment in post with smooth software curves.
MixPre-3II ON/OFF switch is another thing that feels like total disaster after you spend some time to operate the unit. Too tiny, too close to USB-C port, extends not enough to grab it well. And it was not enough pain, so designers choose button with pure black color to make it hard to see on black panel.
They could to use simple "press and hold 2 seconds" on/off button and place it front panel instead SD logo.
Cool thing about 32 bit is that some audio apps can render output to similar "clipless" 32 bit or even double precision 64 bit float. In my example Cockos Reaper
https://www.reaper.fm/ render settings:
Another app Rogue Amoeba Fission
https://www.rogueamoeba.com/fission/ also can read, trim and write 32 bit float WAV files natively. But it is limited only by lossless trimming option. It can't normalize 32 bit files or do any other proper effects itself.
So formally it is possible to keep full workflow in 32 bit.