We know the knots are the most important part of the TzitTzit. No matter which method you use to tie them:
How tangled is too tangled for the strings of the TzitTzit?
What is the definition of tangled vs knotted?
The Kitzur Shulchan Aruch (which brings from many different sources) gives very exact details on how to tie the knots for tzitzis. Yes, the minimum is one knot (and one chulya), but ideally there is a certain specific arrangement.
The idea of tzitzis not being tangled is (to my understanding) primarily after the section of knots (which should be 1/3 of the entire length). So once all the knots that are necessary have been tied, the strings should hang freely, and not be tangled or knotted.
The Shulchan Aruch HaRav says, "the word tzitis can only refer to separated strings. Therefore it is important to separate the strings before making the Bracha".
How tangled is too tangled? To my understanding, any entanglement that prevents each individual string from hanging freely, i.e. by itself. So if two or more strings are tangled in a way that they're stuck together, or one or more strings are knotted beyond the "knot section", then that's too tangled.