1. Although it's trendy to reject Q these days, it remains to me the more likely hypothesis. Luke's version of the relevant sayings usually just seems more primitive to me, suggesting that Matthew was not his source for them. (The main competing option right now sees Luke using Matthew and Mark as sources rather than Mark and Q.)
2. I was reminded yesterday of the two sayings regarding "the wisdom of God" in Luke:
Luke 7:35: "Wisdom is vindicated by all her children." (making Jesus a child of wisdom)
Matthew 11:19: "Wisdom is vindicated by her deeds" (implying that Jesus is wisdom)
Luke 11:49: "The Wisdom of God said, 'I will send them prophets and apostles...'"
Matthew 23:34: "I send you prophets and apostles..."
Which is more likely? Did Luke decide to de-Jesusify Matthew's sayings and make them be about God's wisdom? Or did Matthew take Q sayings about wisdom and equate Jesus with it? Consider that Matthew 11 has Jesus saying something that Sirach has wisdom saying, suggesting that Matthew has a repeated tendency to equate Jesus with God's wisdom.
3. I don't think there's really any ambiguity here. It is much more likely that Matthew edited the version in Luke to equate Jesus with wisdom than that Luke moved away from equating Jesus with wisdom. This is not definitive evidence but it is one example in a cumulative case.
In the end, those instances where Matthew and Luke agree against Mark can be explained by oral traditions. And, of course, Luke may very well have known Mark, Q, and Matthew.