Monsters you control

If a cards text says it effects monsters a player controls does that include face down monsters? For example Red Dragon Archfiend is on the field. Aswell as a face down I control. I don't flip and attack with my face down. Is it destroyed by Archfiend's effect?

"Cards you control" always means all cards on your side of the field, which is narrowed down by additions, like "face-up"

There's one exception, Orange Herald, which says "An effect of an effect monster you control", which is confusing because it means an effect he controls, instead of a monster he controls. (Meaning it works on any effect, not just field effects)

all cards on your side of the field = Cards your control
even u summon it in MP2, it is still destroyed by RDA's effect

Herald of Orange Light is an example of fail translation made by Konami.