You may use IceVM or other skinnier window manager or you just need to set your resolution with your own ways. Xrandr can do just that.

xrandr

You get a list of outputs and modes in the likes of this

Screen 0: minimum 8 x 8, current 7680 x 1464, maximum 16384 x 16384
GPU-0.DP-0 disconnected (normal left inverted right x axis y axis)
GPU-0.DP-1 disconnected (normal left inverted right x axis y axis)
GPU-0.DP-2 connected primary 2560x1440+2560+24 (normal left inverted right x axis y axis) 597mm x 336mm
   2560x1440     59.95*+
   1920x1200     59.88  
   1920x1080     60.00    59.94    50.00    23.97    60.05    60.00    50.04  
   1680x1050     59.95  
   1600x1200     60.00  
   1280x1024     75.02    60.02  
   1280x800      59.81  
   1280x720      60.00    59.94    50.00  
   1152x864      75.00  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   720x576       50.00    50.08  
   720x480       59.94    60.05  
   640x480       75.00    59.94    59.93  
GPU-0.DP-3 connected 2560x1440+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
   2560x1440     59.95*+
   1920x1200     59.88  
   1920x1080     60.00    59.94    50.00    23.97    60.05    60.00    50.04  
   1680x1050     59.95  
   1600x1200     60.00  
   1280x1024     75.02    60.02  
   1280x800      59.81  
   1280x720      60.00    59.94    50.00  
   1152x864      75.00  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   720x576       50.00    50.08  
   720x480       59.94    60.05  
   640x480       75.00    59.94    59.93  
GPU-1.DP-0 disconnected (normal left inverted right x axis y axis)
GPU-1.DP-1 disconnected (normal left inverted right x axis y axis)
GPU-1.DP-2 connected 2560x1440+5120+0 (normal left inverted right x axis y axis) 597mm x 336mm
   2560x1440     59.95*+
   1920x1200     59.88  
   1920x1080     60.00    59.94    50.00    23.97    60.05    60.00    50.04  
   1680x1050     59.95                                                                                                                                                                                                             
   1600x1200     60.00                                                                                                                                                                                                             
   1280x1024     75.02    60.02                                                                                                                                                                                                    
   1280x800      59.81                                                                                                                                                                                                             
   1280x720      60.00    59.94    50.00                                                                                                                                                                                           
   1152x864      75.00                                                                                                                                                                                                             
   1024x768      75.03    60.00                                                                                                                                                                                                    
   800x600       75.00    60.32                                                                                                                                                                                                    
   720x576       50.00    50.08                                                                                                                                                                                                    
   720x480       59.94    60.05                                                                                                                                                                                                    
   640x480       75.00    59.94    59.93                                                                                                                                                                                           
GPU-1.DP-3 disconnected (normal left inverted right x axis y axis)              

or in virtual environment something like this

Screen 0: minimum 320 x 200, current 1024 x 768, maximum 8192 x 8192
Virtual-0 connected 1024 x 768+0+0 0mm x 0mm
   1024x768      59.92 +
   1920x1200     59.88
   ....

Outputs are the names before each resolution list, such as GPU-0.DP-0, GPU-0.DP-1, GPU-0.DP-2 or Virtual-0, Virtual-1 etc.

Available resolutions are under the outputs. We're interested in the first column.

You can change your single output resolution by typing

xrandr --output <output> --mode <mode>

In the first example this would be like

xrandr --output GPU-0.DP-2 --mode 2560x1440

Or with the virtual guest something like this

xrandr --output Virtual-0 --mode 1920x1200

That's it! Put it in your rc.local or just run it when you start your session.