The complexity of OneNote is what makes it so powerful. I use it on Windows, so it's incredibly powerful there. The Mac OneNote client is not really complex. It's basically a Mac Port of the OneNote Web App/Windows Universal App.
The ability to create Spreadsheets embedded in notes to track training without linking to external files, embed files (Pictures, Videos, etc.), link to other Notes in the Notebook (similar to a Web URL, but only for the Notebook) and integrate Directly into Outlook (Notes linked to Calendar Events i.e. Practice Notes for a specific Practice Day) is powerful.
If you don't require what OneNote offers then yea, it can seem overbearing, but if you require even a bit of it then it's going to be heads and shoulders above what this offers, and then some. OneNote can completely replace this, but this can't even come close to replacing OneNote. That's why I'm going to stick to OneNote - because it can grow with me and the way I use Note Taking software. This... can't. It's basically Google Keep for iCloud, and that's simply not even close to being enough for serious use - speaking objectively, because it clearly isn't.
That being said, it's still a massive improvement over what they currently have.
Never had any issues with Laggy typing in OneNote. I believe the editor in OneNote is based on the Microsoft Word editor (similar to Outlook) so it's kind of hard to believe you'd have issues typing in OneNote when Word works fine and is a more complex application. Unless you mean the Mac App. All of the Office Apps on Mac perform kind of bad. That's the price of using them on a Mac
I don't use OneNote for Mac. It's missing all of the features that make OneNote good, which makes it virtually impossible for me to use, since I require those features for how I use the software.