Keep in mind JBs idea of free will =/= Fate's version of free will. they're a little bit different.
JBs version of free will is the difference of having a choice or not. Angels have a choice, albeit a limited one compared to humans. Angels can choose to fall - and sometimes do, although it's not much of a choice as far as angels are concerned. Mab on the other hand literally doesn't have a comparable choice - she and other Fae cannot simply choose to fall, or to lie, or to cheat, or to stop being. It's not that they wont, they simply cant, even though I think in some cases they might like to.
FATEs version of free will on the other hand is the ability to act outside of your nature, which is similar, but not the same thing. The idea is that your power slowly pushes you to make certain decisions and, if you don't have enough will to overcome your power, you become a slave to that power. It's both a balancing factor and narrative. Theoretically, a character with negative refresh could occasionally override their nature, but it gets more and more rare as they go along.
So, to answer your original ops question: JBs version of Will-less? Playable. Fates version is unplayable both for balance reasons and because in the long run not being able to control your own character would be boring.