I barely know anything about turning, but someone said to use the a one that you are comfortable with and gives you the results you want. While it sounds vague it is accurate. I hadn't turned anything in a while and when I was roughing the the last piece of wood to round I tried all kinds of gouges. That particular piece had a fairly deep injury in the side and I had to find one that didn't make it worse. Again, sharp is good., dull is bad.
There is a difference in cutting with and across the grain. Keep you tools sharp and experiment. I use a bowl gouge with a fingernail profile for my attempts at bowls, etc but not pens. That's because I was taught to use different tools for each in class. I don't have a tool identified as a scraper, but several tools which will work as such. I use the fingernail profiled gouge as a scraper on the outside and a gouge on the inside. I'm not great at either and find it difficult to hollow a form thats fairly deep but narrow with any tool that I have. When I get the pictures loaded of my last piece you will see that I didn't get the inside or outside as smooth as "it should be". It's a learning process. I just wanted to successfully get a piece completed. It didn't have to be perfect, I just needed to know that I could basically turn something from beginning to finish. I know what I needed to have done to have made it better. Again, a learning process. I wanted it to be perfect - don't we all? Oh well.
You can, and I recommend, watch many different people and videos of different people but the only thing you will probably find in common is to keep whatever tool you are using sharp. This means that you'll probably need to sharpen you tools several times during a project if it is larger than a pen.
Get some wood and just experiment. Try both kinds of gouges. I wouldn't recommend grinding everything one way or the other before you've used each and know what gives you the results you want.
That's my $.02 worth. Sorry for the length.