They have a few exceptions to Westminster's position which include women deacons, a one kingdom view, tithing as a part of worship in the service, and a few others, not a couple. Their covenanted testimony expands the 35 page confession to almost 400. You have to read through it to see their additions and changes.
The two I was aware of were rejecting the last sentence of 24:4
"The man may not marry any of his wife’s kindred nearer in blood than he may of his own; nor the woman of her husband’s kindred nearer in blood than of her own."
And the latter portion of 23:3 regarding the role of the civil magistrate, though I will say that in my personal, albeit limited, experience the number of exceptions to this exception are growing pretty significant.
I'm not sure what Matthew means by one-kingdom view, and as for women deacons and tithing, I'm not sure either are actually in the WCF, but perhaps the supplemental documents. I will say in practice that both vary from congregation to congregation.
And that said, I would like to point out that we are one of the few denominations who still hold to sabbath keeping and psalm singing. No denomination is perfect but I'd like to focus on the positives here