Any content on the flash drive will be deleted.
It gets longer battery life but also does everything Windows normally does, including running the full range of software and being deployed through Autopilot or Group Policy, managed through Microsoft Endpoint Manager or Configuration Manager and updated through Windows Update for Business or Windows Software Update Services.
To test Office for Windows on ARM, you need to be an Office Insider and running a preview build of Windows 11.
To see if your device will work, check the hardware manufacturer's website or your mobile operator's website.
Windows 10 on Arm uses a system called CHPE, compiled hybrid portable executable files, which are specially compiled ARM64 code that can be called by x86 code without having to go back and forth between 32-bit and 64-bit data types and Intel and Arm conventions all the time.