Gmail Privacy Settings

Click gear icon on top right > See all settings

General

Undo Send: 30 seconds (Not necessarily a privacy feature but might come in handy)
Images: Ask before displaying external images
Grammar: Grammar suggestions off
Spelling: Spelling suggestions off
Autocorrect: Autocorrect off
Smart Compose: Writing suggestions off
Smart Compose personalization: Personalization off
Smart Reply: Smart Reply off
Smart features and personalization in other Google products: Off