As I read from the past posts, each quill is 10% bonus.

Depending on the V&V and province income, I will consider replacement or just leave it as is.

I would replace a 5-6 accumen with corrupt V&V (-20% to -30%) by a 4 accumen no V&V.

If the province doesn't generate much income, I would leave a 4-5 accumen with V&V that reduce income by -10% to -20% but raise happiness.

If the province generates a big part of my income, I would consider to put a 4 accumen no V&V in power.