1)Higher ranking taxa (above genus) are capitalized and italicized, unless:
2)they are preceded by the rank name, in which case they are capitalized but not italicized.

Examples:
Papaveraceae or Family Papaveraceae
Papaverales or Order Papaverales

Is this correct?

But sometimes I see higher taxa in all caps too, like PTERIDOPHYTA, as well as my preceding examples. How does this fit in?

Pinopyta (conifer class)
Pinales (conifer order)
Pinaceae (pine family)
Pinoideae (pine subfamily)
Pinus (pines)
Pinus sylvestris (Scots Pine)
Pinus sylvestris var. mongolica (Mongolian Pine)

Note also that indicators of infraspecific rank (subsp., var., etc.) are not italicised.

A very small number of scientific publications use italics for all ranks, but this is rare.

Using SMALLCAPS for various ranks is also occasionally seen, but again, rare.

Resin