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Ga4 does not give us an api or a way to access the right level of data needed

Thanks! How is it different from https://help.vwo.com/hc/en-us/articles/17441211466009-Integrating-VWO-With-Google-Analytics-4-GA4 and https://docs.developers.optimizely.com/web-experimentation/docs/integrate-google-analytics-4-ga4 and others. These seem to be only using GA4 and not BigQuery. Does GB use a different architecture compared to competitors?

It is a different architecture. GA4 doesn't provide access to the raw data, so you're getting aggregated, sampled data. In contrast, BQ provides access to the raw event data, which results in more accurate experimentation.