Should I be setting my section sizes for the desktop website to 1920 x 1080 pixels?
Hi, Margaret_Miedlar !!
Are you using the Wix Editor or the Wix Studio Editor for your project? If you prioritize responsive design, it is recommended to use the Wix Studio Editor, which allows you to create optimal designs for each breakpoint. 
However, regardless of which editor you use, the most important step is to determine which screen size (breakpoint) you want to optimize your design for. For example, if your goal is to create an optimal design for a screen size of 1920×1080, it would be most efficient to use that size as your starting point. 
Thank you so much onemoretime!