Flexbox? That's way easier than float design and both of those are way easier than designing everything with tables.
Thankfully with modern browsers nowadays you can open up their dev tools and use them as a 'scratchpad' to play about with CSS.
Breaks it down into simple pieces and explains with clear diagrams.
Tables require two (sometimes more) separate reflows. Minor changes in one cell can potentially force the entire table (and all its contents) to re-render. I also don't miss the days of slicing up images into tables for the performance and load-time gains either.