Google Sheets can’t be written from PHP without a Google Cloud project — so PBJ Sheets Sync ships with a small Apps Script “bridge” you install once in your own Google account (about five minutes, numbered walkthrough included; it’s in the bridge/ folder of your download). Every synced row carries an _id and an _updated timestamp; when you edit the sheet by hand the bridge stamps the row, and at sync time the newer side wins — per row, not per table. Backups are simpler still: the whole table is rewritten to its tab on every sync, and sheet edits never touch your database.
Updates are one-time-purchase friendly: your license key (emailed after checkout) unlocks automatic updates for 3 sites on the current major version. The plugin itself never locks up — keys gate updates, not functionality.