Yesterday I was trying elementaryOS with a liveusb and I noticed monitor 1's space was taking a thin string of space of monitor 2, I tried fiddling with the display settings and resolutions but didn't found a fix
You totally ruined my dual monitor setup for me because I immediately noticed the same issue after reading your question. In my setup, this might be related to the proprietary NVidia drivers and the different resolutions of the monitors. I found the easiest way to fix this is by using ARandR. The best tool to apply this configuration whenever connected to the external monitor is autorandr.
- Install ARandR and autorandr with the following command in Terminal.
sudo apt -y install arandr autorandr
- Open ARandR from the Applications Menu. ARandR will show your current monitor configuration. My default, dual-monitor configuration is shown below. My primary monitor is the external one, HDMI-0, which is positioned to the left of my secondary monitor, LVDS-0. The slight overlap appears on the left edge of my secondary monitor, LVDS-0, though this overlap is not reflected in ARandR.
Tip: You can increase or decrease the layout's size from the View menu.
- Click and drag your secondary monitor a smidge away from your primary monitor. In my case, I clicked and dragged my secondary monitor, LVDS-0, and moved it slightly to the right like so.
- Click the green check mark to apply your settings.
This removed the overlap in my dual monitor setup.
- Now, you'll probably want to have this overlap fixed whenever you connect to this external monitor. This is where autorandr comes in. From the Terminal, save the current autorandr configuration with a descriptive name. Here I save my current configuration with the generic name external.
autorandr --save external
Now the overlap should be fixed whenever my laptop is plugged in to my external monitor, at least for my user account.