If it's the same system as previous years it should be 3 matches per mod. Though saying bo5 mods is slightly misleading considering you can play them out of order and end up winning 8 matches total without playing all matches of a mod (e.g win once on 3 main mods, 3 times on the bonus and twice on the last mod, effectively only "winning" two of five mods.)

Unless it's the case that this year we're deciding wins per mod win rather than total matches won? (meaning individual matches are worthless and the overall mod win determines the winner)

Would be nice to get some clarification, I'd assume it's the first thing I said considering it's been that way the previous CLs. If this is the case saying first to 8 wins out of 15 matches might be a bit less confusing.

Sorry if I've misinterpreted something.