Journaling Just Works

The question was not for me, but maybe I can share my pov:

In my opinion most of this overlaps with PKMS. What things belong in a PKMS that don’t go in a journal and vice versa?

There is no hard-coded rule and everythign go go in either one. But I think you already noticed the difference yourself: it's all about the purpose. Which to me is very different in one and in the other. My journal is about free writing while the Zettel is about connecting (and maybe managing) stuff.

In my journal, I do not try to connect anything, or to manage it in anyway beside the dates. I write freely, a few words or a dozen pages if need be and I sketch. In my Zettel, each notion or idea has its own card and since it's analog (real paper cards) each note is also space-limited (I can't write dozen of pages on a single A6 card), which helps me a lot to either summarize more any idea that is not short enough, or will force me to split it into as many logical/meaningful independent units (and in as many cards) as needed so I can then later play with them more freely.

That Zettel is not something I will ever read linearly from first to last card, unlike my journal. It's only there to help me re-read those cards while I mix (a selection of) them in different/unexpected ways, and therefore create new ideas, aka new connections.

I consider my journal fully linear while my Zettel is non-linear, but they both contain the same kind of things: stuff I'm interested in enough to be willing to write about. I will just not write the same way and not with the same objective.

Already looked into Zettelkasten awhile ago. Seems cool but I am getting by just fine,

It's just there if you need it. What's great though is that you try it (and use it too) very simply without much effort.

especially because there’d be a cost to redoing my PKMS that way,

You don't need to 'redo' all your existing content to begin with. You simply need to start using your Zettel with new ideas/projects and it will slowly, organically grow. Say, the next book you start reading, you decide to take your reading notes in the Zettel, and then your own ideas, you put them in the Zettel too, and so on. It will work with you, at your own pace and it will respect your own limits. But, clearly, you don't need to use it at all, it's just there if you want to give it a go ;)

It can also very easily evolve with you and your workflow and adapt to any change in the way you work. My numbering system has changed a lot since I started using it (as my cards changed too, I went from A7 to A6)... That said, I never had to renumber or rewrite a single card, I don't need to. I simply reference old cards by their old numbering scheme and new ones by their new system, they co-exist in peace and harmony. At least with my analog Zettel, that's how it works (without ever forcing me to do anything I don't want or I would consider wasted time)

All of that to say: don't think you will need to redo all the work. You can if you feel like it but you also can just move on. That being said, it's clear the Zettel is just tool among many ;)

Edit: sorry, answered with my mod account, instead of my 'user' account :/