Every place is different. I’ve seen some where you do quick, non-presentable thumbs and functional models for process, then get straight to final presentation/documentation format. Gotta have faith in your designers experience, aesthetic sensibilities, and decision making ability to go that route without having to be wowed by a pretty drawing first.
I’ve also seen some where they want every stroke and page to be client-ready at all times. No thumbs really allowed and all drawings are to be with details well resolved, etc. That seems to be more prevailant when you’re just styling.
Some I’ve seen do almost no sketching at all. Work straight with functional models, getting things to work is most important. Then styling is the quick part you do last after everything else is right.
Some places present b+w drawings, some photoshop renderings, some 3-d models, every place has there own way. You either have to be versatile enough to be excellent with any kind of working style, you find a place with similar workflow to your own, or you work for yourself so you can do it your way.
I’ve tried using the pens and it doesn’t really suit me. I’ve always drawn with a really hard lead pencil all my life, I’m used to that feeling and friction. In recent years I’ve been doing the pen thing because that’s what everyone around me was doing, but results were not very good. I think you’re going to be good at whatever it is that you’re used to doing and have experience in.