Almost all SeraMyu related websites take the same odd approach to informing other fans what the whole musical thing is about - they pour on you tons of useless and insignificant information, like what the name of that guy who was pulling ropes to raise curtains was and when he married and what car he drives, but somehow forget to provide any info on the musical themselves.
Well, I can talk about this based on the perspective of someone who translates the "source material" for information -about- the Myus, not just the Myus themselves. The pamphlets and guides and all that good stuff that we would traditionally consider to be first-hand sources for Myu-information often leave information about the actual musical altogether out. For example, take the S Super Henshin pamphlet. It goes on and on about the production staff and notes from Toei and whatever, and all the blurbs you get from the actresses are either like "Oh I'm new here, wish me the best!" or "I hope I can continue to do a good job playing ______". So if you're trying to glean information about what actually happened in the S henshin musical outside of that, it's pretty well impossible since you don't have the musical itself to work from and what materials DO exist on the topic are pretty...off-topic.
Of course, most musicals do have the source musical for webmasters to view and comment on, but my reasoning as to why no one writes complete guides about them like Wikimoon is because a) people can simply watch for themselves what goes on, b) they feel like they are just writing a summary and c) truth be told, hardly anyone ever really reacts to big long essays. I think the internet has a case of the TL;DR syndrome.
That being said, I find both Wikimoon and Sera-Myu.com and Antics EXTREMELY useful, especially in terms of translation. It's a heck of a lot easier to look up a Japanese person's romanized name (which are notoriously hard to decipher) on sera-myu.com, for example, than it is to spend hours trying to figure it out on my own. If I'm looking to compile a complete list of all the performances of a complete song, Antics is pretty helpful for that. And Wikimoon is great if you're looking for overall summaries of the musicals and cast names and so on, but my only gripe is that it isn't more detailed. I really wish I had more time or a friend to go back after I've translated some musicals and fill in some more in-depth information about the villains / side characters from the Myu as those articles tend to be woefully short. I think out of all the sites, Wikimoon has the most potential to be the most complete, but fans don't seem to use the resource as much as they should.