I mostly use Bootstrap for prototypes. For most of my use cases, I just use card styled divs. There is basic support for different types of container divs in bo

I mostly use Bootstrap for prototypes. For most of my use cases, I just use card styled divs. There is basic support for different types of container divs in bootstrap. There's card-group, card-deck and even card-columns. Never had to go beyond these for my requirements. Forms are a breeze and come out looking great, right out of the box. Bootstrap has a flex (https://getbootstrap.com/docs/5.0/utilities/flex/ https://getbootstrap.com/docs/5.0/utilities/flex/) for managing layout, alignment, grid sizing etc., Also, targeting multiple form-factors and building responsive UIs is easy once you start with the mobile-first styling classes and then start setting the various breakpoints for larger device form-factors. If you already know HTML and some basic CSS, getting up to speed on Bootstrap or Material Design basics might be just a day or so. Their documentation is very good and you can go straight to the section you want (eg: tables) and try it out in your HTML.