For Helix, the rate limit and how to see what your current limits/remaining are in the docs here: https://dev.twitch.tv/docs/api/guide#rate-limits some endpoints have additional limits on top of this which are explained on those specific endpoints in the docs.
One important thing to keep in mind is that the API uses caching, so if you’re making the same requests every 5 seconds you’re making an excessive amount of duplicate requests that are just going to get cached data. There’s no need to make the same request more than once a minute.