Is clinical dental hygiene or dental assistant a good career path?

Yes, but ... I am biased. Just like any career paths, you have to make sure it is what you enjoy doing. Usually we work 4 days/wk, so you will enjoy 3 days off. Dental hygienists will make more $, but they require more training. I would recommend observing or shadowing in dental offices before deciding on a career path.
Career. Both are excellent programs. If you are academically motivated try to pursue the dental hygiene program. You will most likely be in demand. The program is 2 years long. The assistant is also a great position and you will also be in demand if you complete the program which is much shorted. Please observe at a office first to see which you like best. It is best if you have a passion for it !
Depends on you. It depends on what you want and how much you will do to get it. If this is what you wanted to do for a long time, you will likely feel very strongly about it. If it is just something you saw that seemed interesting, then you might grow tired of it being your life's work. It is up to you.