Looks like the $20/month PLUS plan DOES use your data to train the model now... (they seem to have removed that "feature" from the list in the side-by-side comparison)
Chat History is off for this browser. When history is turned off, new chats on this browser won't appear in your history on any of your devices, be used to train our models, or stored for longer than 30 days. This setting does not sync across browsers or devices.
They hide this link a bit. They completed my opt-out request in about ten minutes and at least claim to be not using any of my data going forward for training.
I didn't lose any features like Chat History