Per,
Can its sampler module sample directly
from the real-time live input?
Yes, the sampler (and anything else in Usine) is designed to take any live or prerecorded audio or midi input (or both) and 'do stuff' with it. Live in real-time.
The basic sampler (and grain sampler) module has 'basic' looping features: Play direct from record, overdub, reverse, replace, transpose etc. By chaining multiple samplers together with sequencer or logic/interface modules it is possible to emulate EDP-ish features like multiply and undo. The grain sampler can do Repeater-like time-stretching. It's only your imagination (and patching prowess) that limit how you manipulate what the sampler(s) has captured.
Loopers can do that, but loopers can't be sequenced
like a samplers but on the contrary samplers usually needs audio to be
pre recorded as audio files on the drive.
Usine's sampler modules can loop live audio and optionally save the loops on-the-fly to disk for later recall and/or manipulation.
Ian