If you want shrinking tabs then you can get them in Firefox by putting this in a userChrome.css file:

  .tabbrowser-tab {
    min-width: initial !important;
  }
  .tab-content {
    overflow: hidden !important;
  }

You can find details here on where to find/put a userChrome.css file: https://www.userchrome.org/how-create-userchrome-css.html