Honestly, I don't think you'll find it feels like much has changed at all - modern Rails is still pretty consistent with Rails 4+, modern Ruby is still pretty consistent with Ruby 2+. Its one of my favorite things about the language and framework combo, it feels like once we got past Ruby 1.9.3 and Rails 3 things have been pretty well locked in.

There are new niceties and improvements, but bundler is still bundler, everything is still an object, etc.