The pitch and rhythm suggestions above cover the timbre well. I'd also test what happens when the player presses "show whole line" or switches dialogue sounds off halfway through a sentence. Suppress blips during instant reveal/fast-forward and discard any queued blips, rather than letting the remaining letters sound all at once.
For the separate dialogue slider, route just the text sounds through their own GainNode before the master gain. That lets players silence them while keeping footsteps, UI sounds and music. Fade gain changes briefly instead of jumping directly between values, which can click; MDN explains that here: https://developer.mozilla.org/en-US/docs/Web/API/GainNode
A useful check is a long line, immediate skip, then the next speaker: no leftover chirps and the chosen volume should still apply.