Thanks for this Goran!
The vinyl eraser is for broad stuff and can not be small on purpose. Use the rubber eraser – that is for detail work and can get tiny.
The problems with your line definitely sounds like Animation Paper doesn’t recognise your drawing screen and therefore it is used like a mouse, with low resolution and no pressure. Not optimal at all. Others have the same problems. This is something we must fix. We are looking into it.
Files sizes are not large with Animation Paper either – but I’m sure you are right about similar animation will be smaller for Clip Studio Paint and Krita. One thing is the lasso problem. That does make the sizes very large quickly. But even with out this, sizes will tend to be slightly larger. This is because of the advantages Animation Paper has regarding the line being fully scaleable without any degradation or blurring at all. Also coloring (when that is done) will be much more precise and without any antialiasing artefacts as you sometimes see in other software. In Animation Paper you can also work in a smaller resolution and then change to a higher resolution before exporting – and the result will be super crisp!
Regarding your last comments: All of it is on our todo-list. We are working on doing and improving. I am happy that you like Animation Paper already – and it is getting better! 🙂