I would like to suggest Ventoy for the sake of convenience. You can just copy the bootable images (iso, efi, …) to the drive and boot selectively using the menu. Been using it couple of years, and its a pretty nice solution.
Of course, depending upon where you acquire a package, any software could be considered malware. Always download from the original site, or one that is trusted; that’s a simple strategy to follow to avoid malware.
Balena Etcher is a valid tool for your needs; and is available for major platforms.
Creating a bootable USB from a Windows ISO
The reason for needing this could be e.g. reinstalling Windows but it could also be to update your system firmware - because the vendor only provided Windows binaries - you need a Windows system.
To update you system firmware you can use a Windows PE environment like Hiren’s BootCD Hirens BootCD
If you want to reinstall Windows after your Manjaro adventure get a Windows ISO from MicrosoftTopics covered
Using woeusbUsing ventoyUsing termina1. …