Hey there thought I chime in...
I think any content that's out there you shouldn't charge that would not come off as good especially if it's a fan that's followed you from the ends of the earth, they'll feel like just a dollar sign. What I've been trying to do for my patreon is post the free stuff there so it showcases your comic or art, this is good for potential subscribers.
Any work in progress and concept art I charge and do not share it elsewhere, that would also tick off a subscriber who's paying mula for exclusive content.
People enjoy work in progress and sharing a small story of the progress. I say the best thing to do is plan it all out. It's a good thing you're here asking. I hope this helps and good luck!