Currently it's not much clear which boxes are affected by the outer display type if the element generates multiple boxes. I think it should say that it only applies to the principal box. Otherwise one might think that block ruby generates a block-level ruby container or that inline table generates an inline-level table box.

For example, in outer display type, change

the outer display type, which dictates how the box itself participates in flow layout.

to something like

the outer display type, which dictates how the principal box participates in flow layout.

And also mention it in Outer Display Roles for Flow Layout.

Note: see #1604, it might need to be "the principal boxes" in plural.