The input adjustment on the Midi App goes up to 24 bit only.
Is there any benefit in recording on 32 bit float ?
There are no benefits of 32-bit float for “recording” (and no down-side either apart from disk space, which shouldn’t be an issue these days). The benefit comes when working with the audio after recording. When processing audio, 32-bit float has considerably greater dynamic range, better precision, better efficiency, virtually zero losses, and can survive without damage if an intermediate step pushes the level over 0 dB.
There are currently only two brands that make 32 bit float recorders/interfaces: Zoom and Sound Devices. This is professional gear and priced accordingly.
There is (or was?) also a true 32 bit float interface that’s been around for years. Starting price is way over 12.000 €. The dynamic range is so high the mic input is the line input. No adjustment or attenuation necessary.
32 bit float is interesting for those who record outdoors, like news crews, or nature recordists. No more ruined recordings because things got louder all of a sudden.
For us, mere mortals, 24 bit is plenty.
I’ve been eying a Zoom F8n:
https://zoom.co.jp/products/field-video-recording/field-recording/f8n-multitrack-field-recorder. It was 1.400 € when launched, currently it’s 850 €. Guess I’ll keep an eye on the second hand market for now… 
I’m a bit suspicious of Zoom’s 32-bit claim. They say that it can record as 32-bit float, but I don’t see anywhere in their specifications that they say whether the ADC is 24-bit or 32-bit. When marketing material ‘suggests’ it has a wonderful feature but does not unambiguously say that it has the feature, that raises my suspicions. Nevertheless, the F6/F8 looks like a very nice bit of kit.