New user to Twine here, using the 1.4.2 version. I wanted to make a really sizable story - like, perhaps close to novel-length maybe? - with only a few branches in it. I saw someone mention "story memory" and I was wondering if that meant that Twine has a capacity to how much text it can hold. Which makes sense, but I wasn't sure what that limit might be. So, using some common story as a placeholder, say like the first Harry Potter book, can a Twine story hold that much text?
Worst case, you can write each chapter as a separate twine story and then link them together - there are tools around to let you transfer data (locally) from one chapter to the next.
The slow down is generally a result of having to redraw a Passage Map with lots of boxes and more importantly lots of connection arrows between those boxes.
For my own usage, I like Twee2 very much.