always, blueprints are on a level above the c++ code and requires the engine to convert them to c++. c++ is always faster.
but how much?
it depends, if you have created a mess of a blueprint that has one million references and variables and functions all over the place, it will impact performance.
also if you don’t know c++ and you create the same mess as above, again impact performance.
so the answer to your questions is that good c++ will always be faster. if is good c++
anyway depends of the game you want to build.
I will give you an example. you are trying to build a game that can be compared in similarity with a wooden cart.
Once you will build a game that can be compared with a jet engine, then yeap, your c++ code is crucial.
You are saying you are newbie. go with blueprints first. to do something in unreal you need to know both c++ and blueprints. so learn the easy part first