Though this is a great unit of measure at 1920X1080 and less. Above 1920X1080 things can get slightly tricky, For example when using the Bootstrap8K Theme, If you like the distance at 2REM at 1920X1080 than you’ll want 2.5REM at 2550X1440 or 4REM at 3840X2160 etc
This should go without saying but if you’re targeting higher resolution, Percentages become king. someelement { margin-left:10% } is much better than having to use media queries to change margin-left value for every breakpoint.
On a laptop if it’s 4K the pixel density is increased but your width will be much smaller than 3840 X 2160.