If you are experiencing a very small VM screen size even when you use full screen with VirtualBox - in particular with an Intel Mac - you can try the following steps to troubleshoot the problem.
1. Try shutting down and rebooting the VM. Oftentimes a reboot can fix the problem.
2. If the problem persists through a reboot, make sure you have the VirtualBox Extension Pack installed from the VirtualBox download site. https://www.virtualbox.org/wiki/Downloads If you don't have this installed, please shut down your VM, close and quit VirtualBox, install the Extension Pack, then restart VirtualBox and try running the VM again.
3. If the problem still persists, you can open the terminal inside the VM and use the following 2 commands:
sudo pacman -R open-vm-tools
sudo pacman -S open-vm-tools
If you are still having problems, please send screenshots of any errors you are encountering, full details of what you have tried, as well as what computer and operating system version you are using to email@example.com and the support team will try to help you as best they can.