Rails 6 - What Javascript/CSS Framework is good for me?

Dear community,

since I'm not a good javascript programmer and new to Rails 6 (especially webpacker), I'm looking for a good framework for the whole fancy shit (Slider/Datepicker/Autocomplete/..). Until now jquery ui was my way, but with Rails 6 it doesn't feel up to date anymore.

My research led me to Angular / Angular UI, but I think that this variant is too overpowered, just like React and Node.js.

Which framework do you use or can you recommend for Rails 6?
Bonus: Currently I am using Bootstrap 4.0 as my CSS framework and I am quite happy with it. But maybe there is a good combination of Javascript & CSS framework.

I hope you can help me...good coding...Chris-P-Chicken