Have you ever used a grid system, and if so, what do you prefer?

Before Flex became popular (around 2014), the float-based grid system was the most reliable because it had the most browser support among the alternative existing systems (flex, grid). Bootstrap was using the float approach until Bootstrap 4, which switched to the flex-based approach.

Today, flex is the recommended approach for building grid systems and has excellent browser support.

For the adventurous, look into CSS Grid Layout, which uses the grid property. Grid is a two-dimensional grid-based layout system, compared to Flexbox, which is one-dimensional.