Yes. All seasons of Discovery as well as the first seasons of Picard and Lower Decks are available. Not sure about Yellowstone. It is on my list to try, but it is a long list.
You need at least 4Mbps download speeds to stream CBS AA from what I can find. That seems a bit low to me, but it is what CBS says here:
help.cbs.com
TV shows that are filmed in HD will be displayed in HD on your TV with this service. Star Trek Discovery and Picard will definitely be, but older shows like DS9 will not be since it has not been remastered in HD (yet -- maybe some day).
Yes, it is a good deal if you plan to watch for more than about 5 months. If you only think you'll watch it for a month or so, then not as good a deal.
To watch this service, you will need to install the app onto your SmartTV or a streaming device of some sort. What kind of TV do you have?
Yes. I recommend signing up on your computer and then login on on the TV app. Once you have signed up, open the app, and it will guide you through the login process. I find it easier to choose the "Login via computer" option as that doesn't require you to slowly enter your login info on the TV remote.
I personally recommend commercial-free, but that is a personal choice.