Not the OP here. I’m an outlier, I’ve been using ‚Devon Think‘ for many years and have multiple Databases of PDF to read and markup and other content syncing between multiple devices.

Is devonthink a good option for storing, searching and organizing plaintext? I often make a note while pn computer and save it within a dropbox folder. I have no good way of accessing these quickly on ipad and have wondered if devonthink would solve it.

I used to be a Goodreader user but I like PDF Expert better now. I'd recommend anything Readdle puts out, frankly.

Not the OP, but on my recent trip, I used Apple Books.

The big advantage for me was that I could visit travel websites with lists of things to do, save website as PDF, made annotations of places I wanted to visit.

It synced seamlessly across all my devices along with annotations. I annotated on my iPad at the hotel, and traveled with my iPhone.

Notability is really nice for PDF annotation but not great for reading since it occasionally forgets your position in a book (although there is a bookmark feature). It’s very well optimized: I have over 500 notes in it, some over 1000 pages.

I use Goodreader (but I'm not the one you're asking). It works pretty well for me and syncs with a lot of services.