Pick one source for bidding
Importing GA4 conversions and running a Google Ads tag for the same purchase is the classic double-count. Choose one, delete the other, and keep the rest as secondary.
Why they disagree anyway
Different attribution models, different windows, different handling of modelled and cross-device conversions. Both can be internally consistent and still show different numbers.
What to believe
The store, for business decisions. The bidding source, for optimisation. Reconcile them monthly rather than trying to make them match daily.