I've been disappointed at how limited the pen input is on the iPad. Few apps support it and its built-in understanding of text has a very simplistic model.
Do you know about Scribble? It was new to iPadOS 14, and works everywhere you can write with the keyboard.
I prefer to take notes with a pen. The built in Notes app seems to think you write in a notebook the way you type into one: that each line contains one topic. But in fact when writing notes I tend to make columns of stuff on the right (mostly stray thoughts or TODOs that come up, or list of action items, or an outline, or meeting attendees, or who knows what). I add missing points or clarifications elsewhere and use an arrow to show where they go. Notes agglomerates them all together based on vertical distance from the top edge.
Notability and Goodnotes have some editing that is better than Notes and some that is clumsier. Notability and Soulver and most other apps don't recognize the pencil at all.
What they all need to do is do some actual user research and explore how people use paper and use some machine learning to do a better job of inferring what the user is up to. Some of them (including apple) do that when you draw a triangle or circle but at the end of the day those are just party tricks.
I do assume more effort has gone into the drawing/"painting" capabilities. That's not my use case so I can't tell. But I doubt those applications require or bear the same kind of semantic interpretation that's required for freeform text.