Which of these methods would help you test a manual bidding strategy against an omnichannel Smart Bidding campaign?

Campaign Experiments allow you to test changes to your campaigns, such as bidding strategies, against a control group. This enables a direct comparison of performance between your manual bidding strategy and an omnichannel Smart Bidding campaign to determine which performs better. Geo-X and Incrementality are measurement methodologies, not tools for directly A/B testing bidding strategies within Google Ads. Geo-X focuses on geographic splits for testing, while Incrementality measures the true uplift of advertising efforts. User-based is a broad term referring to targeting or analysis based on user characteristics, not a specific testing method for bidding strategies.