Ive taken online courses.
1. The pacing depends upon the professor.Some courses I've takes have all of the assignments laid out on the first day but with due dates when they should be turned in. In this case its easy to literally complete the whole semester's worth of work in 2 weeks. Other courses are laid out just like normal on campus courses where you are not given notes/exams until the entire class reaches them together.
2. Testing makes usage of your ethics. In an online biochem course I took, we had 60 questions is 55 minutes. That doesn't leave a lot of time to google the entire biochemical process and the fact that science professors utilize clinical based or example based questions for the tested concepts prevents for anyone to just find the info on wikipedia.
3. Prices are usually the same as normal on campus classes.
4. Grading depends on professor, but its usually no different than any other on campus course.
5. I cant speak to any of the courses you listed, but I've taken several online courses, including biochem, genetics and histology and they were as challenging,strenuous and gratifying as any other course I've taken. The only caveat is that in order to get a decent LOR from the professor teaching it, you need to make time to send emails and keep in contact. One way I did this is be emailing questions based off the Powerpoint slides a couple of times per month. I'd even email them with questions that I had after studying the topics in further detail on my own. Anything to show that I was a hard working student and could really use a good LOR.
Hope this helps, please lemme know if you have any other questions.