I'm making an app that works on phones and tablets and allows the users to annotate an image. The user drags over an annotation mark and enters data related to the mark. The user may also draw on the image (Pencil, Arrow, Rectangle, Circle tools). The user would often times put more than one annotation mark per image, highest expected number or marks around 20 but there's no hard limit. The data they enter can be filled in immediately or later when they go back to that image, and usually consists of several (~ 5-10 ct) text fields and checkboxes.
The app will work both on tablet and phone, so the more closely related the two experiences are - the better.
The question here is what would you think is better - a modal pop-up (lightbox) or a slide-in from the side, pros and cons for each approach.
I would greatly appreciate adding quotes from studies or authoritative sources that line up with your answer.
Here's a scribble of what the window looks like:
Option (A): a modal popup with data fields shows when the user drags over an annotation mark:
Option (B): a list of data fields slides in from the side when an annotation mark is dropped: