bqtools functions are the low-level building blocks used to build, deploy and manage data automation solutions, capabilities and products (docs).
bqmanager functions are used to build and deploy tools which support common BigQuery monitoring, management and optimisation activities (docs).
Decode Data for GA4
decodedata-ga4 product enables Google Analytics 4 users to automatically remodel their raw event data in BigQuery based on observed values, making the data simpler to use and more efficient to query. It also enables integration of multiple GA4 properties (docs).