> I haven't yet really tried to commit to one of these Roam-like tools (is there a word for a note-taking tool where every bullet is a nested note, and they can link to each other?)
This is not a "Roam-like tool" by that description. Notes are basically markdown. A bullet might contain a link to a different note, or you could link to several in a bullet or paragraph, or you could link to none, but using bullets doesn't implicitly create nested notes any more than it normally creates separate nested documents in Markdown.
The additional logic seems more built around the directory structure than bullets.
> I worry that, if I used this, instead of a 2-3 big pages on Topic X, I'd have 50 little notes on Topic X, which, yes, I can find through backlinks, but I would not have felt like I had synthesized.
I haven't used Dendron, just barely installed it and poked around, but it seems like the combination of markdown documents and a heirarchical organization alongside a link graph makes it more straightforward to maintain large bodies of maintained/synthesized content rather than small bits of linked content that are easy to navigate but hard to pull together (which tools that focus on linking between small documents as the main structure do seem to encourage.)