I'm sorry, I think I don't understand the second part of the question...
The "WC" stands for "water closet" - so far, so good.
But what was the name for the other common version of this room? Are we talking about a room inside the house were you do your "business"? Apparently it was not "toilet", because a "toilet" was an outhouse back then...
Wikipedia says:
This room is commonly known as a "bathroom" in American English, a "loo" in British English, a "washroom" in Canadian English, and by many other names across the English speaking world.
Source
When you say "other common version of the room", do you mean a version with a bathtub? Is it
"bathroom" then?
In the source below the word "lavatory" is used, but I think that word is pretty uncommon in the US - while the word "bathroom" seems to be as "ubiquitous" as the term "WC" is.
Source
In the following source there are several words for that important yet rarely boasted place inside each modern home, which I had never heard before, like "crapper" (a reverence to the inventor of the flushing toilet, Thomas Crapper) and "john". Learned something new here, I never knew that so many words existed for so tiny a room!
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Something tells me that my answer is too simple, but as I'm "standing on the hose" as we fittingly say in Germany, my answer for the second part of the question is as simple as it is common.
I'm going with "bathroom".
Would you excuse me now for a moment. I'd like to wash my hands ...