1. Understand what you are trying to turn off
Google's wording makes this harder than it needs to be. An AI Overview is the generated summary that can appear above or among ordinary Search results. AI Mode is a separate conversational Search experience where you ask follow-up questions and continue a research thread. Search Labs is Google's testing area for experiments, and an experiment may change how often you see generative features without controlling every AI feature in Search.
That distinction explains why turning off an experiment may not remove every summary. Google says that turning off the AI Overviews and more experiment will not disable all AI Overviews. It is a useful control when you opted into the experiment, but it is not a promise that standard Search will return to a pre-AI layout. Start by identifying the surface you are seeing instead of trying random Gemini or Chrome settings.
There is also a difference between hiding a feature for one query and changing your account experience. Selecting Web changes the current result view. Turning off an experiment changes an eligible experiment. Using another search engine changes the provider. None of those should be described as a permanent global opt-out unless Google explicitly offers that control to your account.