I have spent a lot of time reading and researching how folks are doing fluid type these days. I’ve settled on Uptopia because it doesn’t force any classes or markup. It’s not a “framework.” I also like it’s built in support for PostCSS. Set a few defaults and it generates a fluid type and spacing system in the form of custom properties. Variables you can apply to your existing markup. Instead of guessing with em for padding or margin you have a consistent step scale to work with.