“Mobile first” is Bootstrap 4’s motto. Meeting mobile demands under TYPO3 is not easy, but it is possible. Bootstrap 3 offers objects and layouts that are easy to use in order to help the developer attain that goal.
For TYPO3 developer: flexible expandable!
The advantage of Flux lies in the power of Fluid, which it is based on. Flux uses its abilities for the TYPO3 back-end so that new objects can be built by creating Fluid templates. There is no need to do mapping or to use TypoScript Code. Even whole extensions like Slider can be made obsolete.