Should I create C++ or BP project for a C++ only project?

I’m planning to use only C++ and use Blueprints unless it is absolutely necessary like animation blueprints. So I think blueprints still will be used at minimum(I’ll try to not use if possible, ofc). So the question is: should I have to choose C++ or Blueprint when creating new project in Launcher?

No difference between the two. A “C++” project has project sorce code generated for it from the start.

If I choose C++, then can I create and use Blueprints?

Yes. If you want to use Unreal Engine properly, you’ll use both anyways. Think about Blueprints as the final layer, the link between your code, and the game. This is where you’ll fine tune variables, expose functions/events so that designers (or you, or anyone else) can add that final polish.