Does Storage Studio permanently delete anything when uninstalling?
Short answer: No. Uninstall moves everything to the Trash, so it stays recoverable until you empty the Trash yourself.
No. Everything Uninstall removes — the app and any leftover files you leave ticked — is moved to the Trash, never erased directly. You can recover it until you empty the Trash yourself.
The same is true of Remove on the Offloaded tab.