CotEditor is great. I've been using it for years, though not as my primary editor. It feels like a spiritual successor to TextWrangler. In some respects it feels a little old-school in that it's not afraid to use multiple windows. For instance, CotEditor's Find command still spawns a separate floating window, which used to be ubiquitous in Mac apps but has all but been entirely supplanted by the inferior waste-of-space-randomly-attached-tiny-UI carbuncle search that now infest even the likes of TextEditor.app and Terminal.app.
The creator/maintainer is also quite responsive to suggestions. I managed to convince him to make CotEditor support Cmd-Shift-[ and Cmd-Shift-] for switching between tabs by pointing out that although they're not the canonical forms (that would be Ctrl-Tab and Ctrl-Shift-Tab respectively) they're much easier to use and supported by pretty much all programs that even have multiple tabs, from Chrome to TextEdit.
From my experience/workflow, it's because I typically am needing to switch between reviewing the contents of a file and changing my search up a bit based on what I'm seeing. To be clear, for extremely bulky logs or projects, grep + sed + awk are my go-to since even the best text programs have issues with multi-GiB sized files and I want to heavily manipulate the output, but sometimes that's overkill (and when training employees, the same result can be achieved without the burden of having to learn these programs; eventually they will learn, but it's burdensome and additional stress when they have far more important things to be learning when they start)
When I do searches like that, the tool needs to be there and powerful when I want it, but also immediately out of the way. Notepad++ handles this really well IMO by letting you adjust the transparency of the search and having a lot of power to it, the only blemish being how np++ wants to try to lock the search to the main window (which I'm sure can be disabled, I just never took the time to figure out how). But there is so much you can do with the search that it needs space to show its options and power, and that takes up space from the document which means now I have less on the screen to review. This is annoying even on an "okay" sized monitor, and exacerbated on a laptop monitor.
Sometimes I just open Sublime instead of TextEdit because Apple's own less-featured text editor takes much more time to launch than a third party editor with more features like Sublime Text. Not to mention that I need to hit Cmd+N to open a new window to start writing.
3 or 4 years ago I was trying to find an editor that wouldn’t take an unreasonably long time to open a very large log file.. believe it may have been a couple hundred meg or even close to a gig really can’t remember exactly. What I do remember though is CotEditor was the only one out of maybe 4-6 others that opened it very quickly (maybe 1-3 seconds— again quite some time ago). Even vim took way too long to open it…
CotEditor is great particularly for me because it's developed in Japan and thus handles all the relevant international text issues properly. Automatic encoding detection, mixed-script text, even vertical script!
When I was using macOS regularly, CotEditor was my go-to text editor before I learned Emacs. Compared to XCode, Netbeans, and Eclipse, it had a miniscule memory footprint (somewhere between 10 and 20 MB). It wasn't as fast as Sublime for some tasks, like regex search, but had built in syntax highlighting support for nearly every programming language still in use, and it was very easy to create your own themes, with an intuitive graphical interface for setting colors for different token types.
Comparing it to default text editor I think is not correct, try to compare it to another code editor like VSCode, Nova, etc... it's very fast and simply, I love it.
For what subset of notepad++'s features? I've known a few users, and their patterns range widely. Some hinge on one specific feature, others just want a basic syntax highlighting editor that doesn't fight the system (i.e. Electron, gtk, vim, emacs).
TextAdept worked for the lightweight side, as it also uses the same Scintilla editing core. But way less menu entries and customization features.
CotEditor and BBEdit's basic feature set (that replaces TextWrangler, although you can even still use the same icon) might be appropriate.
But yeah, if you're really into some aspects of notepad++ or depend on special features, it's hard.
Have you tried UltraEdit? I used it 10 years ago, so I don't know how well it has aged, but I preferred it over Notepad++ at the time.
The reason why I don't use it now is because IntelliJ and vscode covers most of my need, and it's hard to justify the extra expense at my work place. I sometimes miss how well UltraEdit worked in multi-column mode and hex edit mode
This is something I always noticed with the Mac app ecosystem. Even sometimes the most basic apps are paid. Windows and Linux has a much better free/FOSS and freeware app selection BY FAR.
The creator/maintainer is also quite responsive to suggestions. I managed to convince him to make CotEditor support Cmd-Shift-[ and Cmd-Shift-] for switching between tabs by pointing out that although they're not the canonical forms (that would be Ctrl-Tab and Ctrl-Shift-Tab respectively) they're much easier to use and supported by pretty much all programs that even have multiple tabs, from Chrome to TextEdit.