Hey yannig,
I think you’ve made the right choice here

I was looking into TXP quite seriously as, like you, I liked the tag + template flexibility. But then I found MODx which can do all that, but also has these awesome custom fields called Template Variables which you can use to add anything you want to a page. Also, no having to explain to clients that ’articles’ are actually pages on their site even though they don’t have a news section. I’ve not looked back and use MODx for almost everything now.
I think you would be fine starting with either Revo or Evo as each version is only as complicated as you want it to be. Both can be used for basic sites or custom coded applications, although Revo is certainly the way of the future and extremely flexible for developers.
That said, for a beginner I would probably recommend starting with Evo to get a feel for how MODx works. There’s a bit more documentation available, more add-ons and several years worth of troubleshooting available on the forums. And it’s pretty simple to switch over to Revo when you are up to speed
I was going to suggest the links that goldsky has given you as they are very easy to follow. The
official docs also come in handy.
And to answer your question - ’101’ is generally the course number given at universities for introductory units in first semester, first year units. It’s quite commonly used to describe some kind of beginners activity. Welcome to MODx!