Do focus effects need to be activated before determining the value of each focus pool? For example, do I need to activate the Ring of Fire's -2C reaction before I know how large a focus pool my opponent has? And what if both players focused a Ring of Fire (more of a timing question, there)?
focus effects
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Do focus effects need to be activated before determining the value of each focus pool?
I'm guessing that by "focus pool," you mean the total number of cards focused. "Focus pool" is a game area with Fate cards that can be used during a duel.
http://rules.l5r.com/Challenges_and_duels:
"F: Focus Effects resolve. ...
"G: Both Personalities in the duel compute their score for the duel."
Yes.