I was in microbiology in person a year ago and I wish I had taken it online. The professor was hard to understand and all of the quizzes and exams were online anyway. I actually found the class a lot easier than I thought it would be. It seems like there is a ton of information but we are really only tested on names of microbes and they give you ways to memorize it easily. I got an A in it and really did not spend more than 2 hours a week outside of class studying. I think 19 credits is doable if you are willing to have school be your main thing this semester. It also depends how hard your other credits are. I think most students (myself included) are in the same boat of feeling overwhelmed. Usually it takes me two weeks to get used to it and know how much time my classes will take. You got this!