Integrations by system
Start from the system that already holds the record.
HubSpot is one side of the map. The other side decides the objects, the direction, and the failures you will actually see.
ERP
SAP, NetSuite, Dynamics, Odoo. The legal name, the order, and the invoice stay there. HubSpot receives the slice sales and service need.
Ecommerce
Shopify and the rest. Match the customer before you create one. An order is not a new person.
Finance
QuickBooks, Xero, Stripe. Paid, failed, or refunded. The line detail stays in the ledger.
Warehouse and BI
Snowflake, BigQuery, Power BI, Looker. HubSpot is a source. The join lives in the warehouse.
How you connect
Native when the objects already match. iPaaS when a person can read the scenario. Code when the map is the product.
Direction
One way for invoices and legal names. Two way only on fields with one owner each.
Name the system of record first.
If you cannot say which system wins when both sides change, the connector will decide for you. That is how duplicates start.
See the usual breaks