If God knows everything, you basically have five types of explanations when it comes to free choice in saving faith:
1. God sees into the future and knows your choice. So his decree to create includes your choice. (Arminian)
2. God has middle knowledge, knows all possible worlds, and selects the one that both guarantees creaturely freedom and occurs just as God wills. (Molinist)
3. God causes everything. He is the pool cue. We are the billiard balls. (Determinist)
4. God ordains genuinely free acts since he, as First Cause, acts in a way that transcends the physical ordering of things. He is first cause to our free choices, not in time nor in physical order, but in a way that only can make sense to God before whom all things are present in his timeless eternal existence. (Early Reformed / Reformed Orthodox)
5. God ordains all things, but he does so in a way that is compatible with human free choice. So God determines all, yet does so such that humans experience genuine freedom (compatibilism).
The difference between positions 4 and 5 matters once you get into the more detailed explanations of what is a free choice and what is free will. For me, a free choice requires a judgment (mind) that the will acts on, which is not determined in one direction. So you could genuinely choose blue or red. Free will is just the faculty of the will, unbounded in its normal functions.
Compatiblism in my view seems too deterministic since it basically requires that God’s will or decree determines a free choice towards a specific end. It at least makes me feel uncomfortable. The Westminster Confession denies that any choice be “determined to good or evil” (WCG 9.1).
I like the mystery of saying: God outside of temporal succession and the order of physical sequence (premotion) ordains and so enables the power (potency) to judge and act in one way or another way, a genuine free choice between alternatives. It may be subtle. And for most people, it won’t matter. But if one thinks about these issues, it makes life much more exciting and livable because it allows me to avoid the sense that my actions are determined toward one end.
Perhaps the best way to end is to quote Heinrich Bullinger’s Second Helvetic Confession (ch. 9, 1562) where he clearly affirms free will and the ability to choose between alternatives:
In External Things There Is Liberty. Moreover, no one denies that in external things both the regenerate and the unregenerate enjoy free will. For man has in common with other living creatures (to which he is not inferior) this nature to will some things and not to will others. Thus he is able to speak or to keep silent, to go out of his house or to remain at home, etc. However, even here God’s power is always to be observed, for it was the cause that Balaam could not go as far as he wanted (Num., ch. 24), and Zacharias upon returning from the temple could not speak as he wanted (Luke, ch. 1).
Free will (the faculty of willing) can choose to one thing or another—it has the power of contrary choice. But God can intervene to impede free choice as he did with Balaam and Zacharias.
Bullinger also condemns the Manichaean notion that the Fall was not caused by our free will:
Heresies. In this matter we condemn the Manichaeans who deny that the beginning of evil was for man [created] good, from his free will. We also condemn the Pelagians who assert that an evil man has sufficient free will to do the good that is commanded. Both are refuted by Holy Scripture which says to the forner, “God made man upright” and to the latter, “If the Son makes you free, you will be free indeed” (John 8:36).
Bullinger represents a stable line of reformed thinking in which people have genuine freedom in external matters. The reformed as a whole do not believe that one can please God apart from faith (Heb 11:6). The will has been damaged by the Fall so that it can no longer please God apart from grace. But all the regular choices in life fall within our power.