I don't know how to decide between the $X$ and $O$ arrangement, i don't have any specific example at this moment, but i want to know.
Catalogues offer only some basic calculations. I'm not quite sure if there any guidelines or instruction exist, i have already consulted many books, but so far my researches failed to help me justify the choice between the two arrangements.
Source: https://debearings.se/wp-content/uploads/2016/08/12-Tapered_roller_bearings.pdf