Responsive Order Component with CSS Flexbox and Grid

This is my first submitted solution! All feedback is greatly welcome. Does anyone have a good tip or strategy for knowing what to use for your sizing units and when? With the Figma file I was able to know exactly what some heights and widths should be, but for responsiveness, should everything be relative only (like rem, em, percentages, and vw/vh)? Or are using pixels, especially for font sizes, usually okay? Thanks!