You can't (easily) downgrade, so if you disable beta, you'll get the next public release of any newer OS version (meaning that if you run iOS 17 Beta, you will not get access to iOS 16.6 when it's release in a few weeks, even if you disable beta software).
If you turn off beta today, your next public release will likely be iOS 17.0 in mid to late September. You will indeed stay on the same beta version you are on right now, and will not be offered new beta versions.
If you wait until the public release, just know that the last beta (called Release Candidate) usually has the same built number as the public release, because it is effectively the same software. So if you install the release candidate on your iPhone, you will not be able to access the public release version. They are effectively the same software so it makes no difference regarding the software experience, but you will be 'stuck' in the beta cycle until 17.0.1 or 17.1 is released.