What are the Apex forms of Lugia/Ho-Oh?

Question

I was looking at the Pokemon Go dex and a word 'apex' caught my eye. I looked at it, and saw that the two birds had the forms.

Answer 1

Apex Shadow Ho-Oh is different than its normal form because it can learn Sacred Fire +. This is a stronger version of Ho-Oh's iconic move that does 130 power in trainer battles and 135 power in gyms and raids. Once it's been purified, Sacred Fire + will evolve into Sacred Fire ++

Source

Same with Lugia but for Aeroblast. They simply have higher attack powers.