Are my handwritten notes uploaded to the cloud or to your servers?

No. The app normally pulls your notes straight off your Supernote over your local Wi-Fi (Browse & Access) and converts them to PDF on your Mac — nothing goes to the app maker's servers. If you use the cloud option, the app downloads the copy your device already synced to your own Supernote cloud account — again, nothing is uploaded anywhere new. The ONLY time a note leaves your machine is the opt-in Google Drive feature: if you connect Google Tasks and explicitly turn on "upload notes as PDFs to Drive", then when a linked task is pushed, that note's PDF is uploaded to your own Google Drive. That's off unless you switch it on, and even then it goes to your Drive, not to us.