NeoReader scrolling/zooming for PDFs on Boox tab X

I recently ordered a Boox Tab X and it came in through the mail yesterday. After playing around with NeoReader on split screen mode, I observed the following:

Assuming I deactivate dragging gestures and disable panning, there is only one way to "scroll" through the document: namely the "Next view" and "Previous view" buttons. However this will automatically jump too far forward in the text. I just want to sort of nudge the document vertically downward, similar to how you would click on the down arrow in a scrollbar.

I'm aware that I can also enable the "Slide/Drag the page" gesture but since I am already zoomed into the document somewhat, it bothers me that I can also slide horizontally. Is there an option to lock the panning only in the horizontal direction so that I can drag vertically? If so that might fit my purposes somewhat...

Finally I'm wondering if there are any alternative e-readers out there with more customizable functionality. NeoReader seems OK for note-taking but the difficulties I've outlined above are hampering my reading/note-taking experience. Also, why is there not a basic zoom feature? It seems I can only zoom in by "selecting an area" which isn't always ideal.