License
When you run Windows in a VM you need a Microsoft Windows digital or retail license as using the firmware attached licence is not valid.
When I tried to activate my Windows with the key from the firmware - Windows responded with a message stating
No valid digital license was found
β Old forum topic
This forum does not endorse piracy so to use Windows in VirtualBox you are encouraged to obtain a valid license.
Performance
High-end 3D modelling, screencasting and extreme gaming will most likely not deliver the performance you are used to.
VMware
VMware is generally unsupported on Arch-based distributions. Providing you follow the Manjaro specific installation instructions it will work - but you should not expect a troublefree experience.
VirtualBox
VirtualBox will give you a rocksolid Windows for daily tasks such as productivity tools or software development and light gaming.
libvirt
A third option is to use libvirt. This option is highly advanced and requires in-depth knowledge of your hardware and is therefore not recommended for casual use.
Recommended
On Manjaro VirtualBox is the recommended virtualization software because it is easy to use and suffice for most use cases.
Backup
The virtual machine(s) are stored as diskfiles and thus easy to backup to external media.