Building a character, compiling it, and rebuilding it after every game update costs nothing and is not going behind a paywall — mods that keep working through Early Access are the whole point. Pro pays for the parts that cost money every month: storage and build time.
Payment is handled by Stripe. Cancel any time from the same place.
If you cancel, everything you have saved stays available to open, download and delete — and every version in its history stays restorable. You simply cannot add new cloud characters beyond the free slot. Data you have already given us is yours whether or not you are currently paying.
Curious what it actually costs to run? The numbers are public.