Joe Morgan probably covered everything. But just in case.....
The cdrom game can be purchased all by itself and you get to play but never see the cards which makes it fairly generic like any other computerized baseball sim game. You can purchase with card images where you can also in additon to all the play features lets you see a "picture" of the card image. For me that is necessary to truly make it strat. Then the ultimate you can also purchase the actual physical cards that you can sort through without a computer and play with actual dice if you desire to go old school.
Technically all strat products are on the cdrom. But what you can see is based on what license keys you purchase and enter to unlock that feature or player set. Each year in theory you will only need to purchase the current cdrom version to go with the newly added 20xx set. Your historical set licenses should carry forward so you keep access to all the past seasons/sets you have purchased.
Why get 5 teams? Because you get a discount. And your experience with any single season could vary considerably. You may have a bad experience with just one team and quit when with a little more exposure would find a great hobby. Just my opinion that just one team is insufficient to accurately judge how much your might enjoy the hobby. Also, since there are multiple types of online strat and each has it's own pros and cons you might like one while not liking another. For example I would never waste time with a mystery card game or the baseball daily game. But there are those who love them. How do you know which one you might fall in? In my opinion best way is to play one of each. So if you play a 20xx game, an ATG game, a mystery set, a baseball daily you have purchased 4 credits. At single credit purchase you have already basically paid what you would for a 5 pack. So why not buy the 5 pack and have that final 5th basicallly free credit?
What does a mystery league mean anyway?
In mystery sets you basically start with a decade. Each player in the set has 5 seasons from that decade. You draft the player but do not know which year you will get. Could be his monster 98 season or it could be his disastrous 95 season. Thus the mystery monicker. He is not in any mystery sets but the Ichiro card comes to mind. One season is balanced toward righty pitchers and another is stonger against lefties. Can you figure out which one you have and manage accordingly. Or maybe you draft Brady Anderson. Did you get his 50 HR season that will crush pitchers? Or any of his other seasons where he will kill your team? Some people love the challenge of figuring that stuff out. Some do not. I think as someone new to the game only way to decide which you are may be to give it a try for a season.
Why did you mention that 365 can get rather expensive.
Because if you get hooked and do not have self control you can end up starting a new team every week and having a $100 a month budget for strat. Or really hooked and be launching a new team every day and having a $100 a week budget. For some of us that is expensive. Think about it you could be looking at playing strat or buying a new car. There was a time I always had 8 teams going at any given time. And there are some who always have 20, 30, or more teams going. If you are not winning a lot of finals so you are doing that on free credits then better have a good job and an understanding spouse.
And last there is no actual real time managing in the online game. You are more of a general manager than a field manager. You construct the team and give Hal the manager your desires but what actually happens may not follow your script. For some the frustration of that ruins the fun. For others who can accept that they have a ton of fun.