I'm designing a long tablet form and trying to decide on the navigation. My intuition is telling me option A in the image is the right approach. It feels like one long form on one page vs. several pages but I don't have anything to back this up. Are there any studies out there or is this something I should test both ways?
Depending on how long form is, it is good to have it clustered in steps.
I would also go with vertical to down behavior, as it is more used and popular to scroll down than swipe.
Having horizontal version would make sense if your users will use tablet in landscape mode. So you maybe can research how often is that, and how often tabet users do swipes.
With the current information: Option A.
Presenting form fields in a single column layout will keep the 'vertical momentum'. Nngroup has a great article regarding web form design. One of the points in the article is:
3. Present fields in a single column layout. Multiple columns interrupt the vertical momentum of moving down the form. Rather than requiring users to visually reorient themselves, keep them in the flow by sticking to a single column with a separate row for each field. (Exceptions to this rule: short and/or logically related fields such as City, State, and Zip Code can be presented on the same row.)
There has also been a study in 'Designing usable web forms'. I only read the Abstract but it should also apply to your current problem and maybe help you solve some new problems.