What size to create a dashboard layout?

Question

Design

In general, the question is, what size to create a dashboard layout (admin panel)? And what mesh should I use?
Given that the left panel is fixed to the left edge, and the screen size is different for everyone. That is, if I make the layout 1920px wide, then when I open it on a smaller resolution screen, everything will look different

Answer 1

what size to create a dashboard layout (admin panel)

Anyone.
Any.
For this, adaptive layout was invented.

Answer 2

codepen.io/GreatRash/pen/Mbpxwo