question

Definitely use only one Title ID. While you could, technically, use a different Title ID for each mini-game, a) it would be a hassle, code-wise, and b) more importantly, you'd be losing a lot in terms of the live operations capabilities, since the player actions would be spread across multiple distinct PlayStreams (the stream of all events for your title, which you can use for automatic actions, doing user segmentation, driving scheduled tasks, etc.).