Mars from Yarn Spinner here, and I’m fairly certain I’ll know what your text speed issue is. Most people assume that the way they set the speed initially in the inspector on the LinePresenter is the same property they need to access to modify it later, but by then that value has just been used to initialize a typewriter object that’s now managing its own speed. So to change speed at runtime, you need to access that LetterTypewriter’s CharactersPerSecond (or the WordTypewriter’s WordsPerSecond) directly. That change will then be applied from the next line onwards.
Hope that helps! :)