New messages always arrive over the WebSocket gateway, from the moment you add the channel. Read past history additionally walks backwards through what was said before — useful for search, but it is the one behaviour that does not look like a browser. Untick it to track the channel forward-only, or set a from date to read back only that far — a short, bounded read rather than an open-ended crawl.
Stored encrypted in data/secret.key. Automating a user token is against Discord's terms and can get the account banned — a bot token is the safe path where you control the server.
data/secret.key