I'm not aware of any training system in which "zone 5" is a training level you can ride continuously in for more than 5-8 minutes or so, at least if you're doing it right. But my knowledge is small, and the world is large.

Still, I think what you're asking requires a more complete and careful answer than you can easily get from a message board. Because I do think you don't even quite know what questions to ask, or how big the question you have asked is. It's really the kind of question that requires a literal book to answer fully. If you are looking to try training with periodization (I think this is what you mean by "polarized"), you might be better served by starting out with something like The Cyclist's Training Bible, by Joe Friel. There may be other appropriate books as well, and I know people around here that have lots to say on some of the details in that book. But nothing else that I'm aware of lays out how to think about and plan training with the same clarity and completeness. It's sort of a cycling training 101. If nothing else, starting from there or another source with similar scope and goals will be less confusing because it will be written from a singular philosophy and voice. At this stage, that's probably a lot more helpful. Everyone here will have different experiences and philosophies and even with the best of intentions, that means that what you get can be a bit cacophonous and confusing.