VirtualBox is another emulator like Qemu. In fact, there is a bit if a love/hate relationship between the supporters of Qemu versus the supporters of VirtualBox. Qemu is more lightweight, while VirtualBox is more feature rich! In any case, let me describe how to set up VirtualBox on your system, and then you can decide.
The VirtualBox application does not come with the GNS3 install. Before you can begin to think about running VirtualBox (VB) emulations, you will have to download and install the VB package from https://www.virtualbox.org/wiki/Downloads. Linux users will also need to also install xdotool.
Assuming you have VirtualBox (VB) installed on your system, you now have to configure GNS3 with the details of your VB installation.
Start by opening the GNS3 Preferences, VirtualBox settings, General Settings tab.
The default settings should be all you need, but make sure you click on the Test Settings button to be sure. If you see a message...