I understand why people prefer traveling alone. If you want to stay an extra day somewhere or decide it isn't all it was supposed to be, you can change plans. Its easier to go to small places as a pair than as a party of 24. More likely to meet locals. And so on.
To pull it off, my advice is to put in as much work as you can upfront. And with a 22-day tour like rick does you're biting off a lot because it means trying to master 10 different areas instead of say 4-5 days in 3 places. You can do it, although I have to admit I'd blanch at the task. With the pair of you, maybe divide up the cities. For example, you take 5 and your companion the other 5. Start with lodging and get that firmed up. Next is transport. Figure out, in detail, how to get from the lodging in A to the lodging in B. "Take the train" doesn't cut it. You need to know how to reach the station, what time the train leaves, cost, etc. Then figure out what sites you want to see, when they're open, where they are, etc.