I am running Ubuntu 14.04 as a host and Windows 10 as a guest in Virtual Box. I used Windows 8.1 as the operating system type when I set up the box. Windows 10 runs fine. I was able to install Guest Additions. However, I can't increase the resolution past 1600x1200.
Well, I can get the box to display full screen if I enable 3D acceleration in the box settings but that has a tendency to crash the virtual machine before it gets past the login screen so I don't use it. The reason 3D acceleration doesn't work I imagine is because my computer has Intel HD 4400 graphics as opposed to a discrete graphics card.
The problem is that my screen resolution is 3200x1800 on a 13.3" screen so 1600x1200 is really tiny.
Every solution I've seen has said to install guest additions, enable auto guest resize, set the global max resolution to "any" but none of those things seem to work.