Took at look at the manual. Was mostly curious about what the input level pots do when the unit is set to 32-bit floating-point recording mode. It does not say. It says only:
Adjusting input levels
Turn the input level adjustment knobs to adjust the
audio signal levels recorded in recording files.
While watching the level meters, adjust the input
level adjustment knobs so that levels average around
−12 dB and the peak indicators do not light.
Recording sounds might distort when peak indicators light.
NOTE:
>If a input level exceeds –2 dB, the peak
indicator for that input will light.
> If an overload occurs with an analog circuit, the
entire level meter will become red.
Since this could cause the recorded audio to become
distorted, make the following adjustments.
> Distance the mic from the sound source.
> Lower the volume of the sound source.
And from the specs:
Mic amp EIN (equivalent input noise)= –127 dBu or lower.
Dynamic range Input jacks 1–4 (MIC IN) to PCM data (20kHz LPF,
A-weighted, JEITA) = 133 dB or higher
^
Based on that I presume analog preamp gain to the dual ADCs is fixed, and the input level adjustment is digital, occuring after the dual ADCs but prior to writing to file. So, if in 24 bit mode it remains necessary to set input levels to avoid clipping the digital output to file, while setting input levels in 32bit-float presumably sets initial playback level (which may be changed in post). That would mean adjustment of the input level knobs does not alter the recorder's noise-floor. It also means any mic-input which exceeds +4 dBu, or line-input which exceeds +24 dBu will clip regardless (input specs in a post to follow).
Implication is that users recording in 24bit mode should be able to initially determine an input gain setting based on the max output level of whatever mics are being used, then leave the input level knobs locked and untouched from that point on and achieve the same effective performance as recording in 32 bit float mode. Just like when recording in 32bit mode such users will need to normalize levels afterward, but won't need to revisit input level settings again until switching to a different set of mics. Set reasonably, there should be no noise floor penalty.
Old school 24bit tapers can set levels higher as they always have which may eliminate the need to normalize, but at the risk of clipping, same as it ever was. But there should be little to no change in noise floor.