Your content type changes the answer here. AI self-insertion into movie/game/cartoon worlds is novelty content — and novelty content has a specific distribution logic that's different from regular music promotion.
The hook isn't "here's my music." The hook is "what is this sorcery?" — and that reaction lives on TikTok first. Your Twitch and YouTube audiences already know you; TikTok is where strangers discover you because they stopped scrolling at something they've never seen before. Start building there immediately and treat it as your top-of-funnel.
On the dump vs. drip question: don't dump, but the reason isn't what most people say. It's not about "seeming spammy" — it's that dumping 20 videos at once means the algorithm has no feedback loop to learn from. Post one every 2-3 days, watch which hooks get the most 3-second holds, then brief your next batch around the formats that stopped people.
For cross-posting tools: Buffer, Later, or Metricool all handle multi-platform scheduling. The key is always to export the native vertical format for TikTok/Reels/Shorts — re-uploads of landscape video with letterboxing die in the algorithm. Your 240 IG followers will grow faster once you have TikTok driving discovery back to your profile.
One more thing: the Twitch audience is your most engaged group. Pin a channel post there whenever you drop something new — even just "new music video out today." They're the people most likely to share it cold.