best practices for establishing links between SQL Servers

Are there any specific do’s and don’ts from a security/overall best practice perspective, when establishing the links between a central ‘data warehouse’ (SQL Server 2019), and the ‘multiple source databases’, also SQL Server Enterprise 2016 or 2019 versions scattered across a domain, that will be providing regular feeds of data into the data warehouse.  

There is essentially a need to populate a central 'data warehouse' (SQL Instance) with daily data feeds from up to 12 databases, hosted on different SQL instances/servers across the network. The security and operations team are currently assessing the mechanics of the data flows, as the databases contain personal/sensitive records, and the data to be transferred is only a subset of records, not an entire transfer to the whole database, just specific tables.