I'd go for the 10% 4 turn. Yes, people do talk about strategies, but as far as I've seen, I'm the only one who RNG abuses in playthroughs. dondon, Horace, PKL, etc. all prefer efficiency as opposed to RNG abusing. In a recent run dondon refused to rig too much (even though he has an RNG viewer) in FE6. Horace and PKL both do efficiency and little rigging, as far as I recall.
My motto is to just RNG abuse as much as I have patience for. But Lyria's songs would have to require rigging in so many chapters, and the line to draw would be so arbitrary and confusing, that it might be best to just ban that completely.