There are lots of different ways to produce texture with brushes - The tip is one, but there’s also texture pattern, various settings such as scatter, rotation and size can be set to increase expression of texture, and the masked brush setting is good for more complex media emulation (like watercolour effects). The new RGBA feature can be used to emulate thick texture - like impasto effects.
Yes - You can create tips from scans of real media, or isolate textures from photographs. I have a set of scanned ink tips I made years ago and used extensively, so I think it’s worth the effort.
It isn’t necessary to have a natural tip though. The tip alone is not what makes the brush behave like natural media - You need to think about the behaviour of the media you are trying to recreate, choose an appropriate engine and tip, then play with the many settings to find the right feel.
Common settings to start with are spacing, angle and rotation (drawing angle or tilt). Size is useful if you want a tapered stroke. Then you have a huge array of other options to fine tune, or create various effects.
Ramon spends a lot of time studying real media and trying to recreate them digitally - so his posts, videos and brushes are a good resource for learning about this. And of course David Revoy, who’s been making Krita brushes longer than most.
I hope that’s helpful in some way and I’m not just telling you stuff you already know!