If you're looking at distributed load off the HQ, use replica downstream servers at each site. If you're looking at creating a single point of connection, drawing all updates from HQ, a single WSUS server will work. If you're looking for creating a single WSUS server for HQ, but having all other sites get approvals from WSUS but download directly from Microsoft, use a replica downstream at HQ, but specifying that updates will be approved only on WSUS but downloaded from Microsoft and setup your Location for each of the sites to use this replica downstream WSUS server (similar to the externally facing WSUS server as linked in my guide below).
Some links of interest:
https://www.ajtek.ca/wsus/how-to-setup-manage-and-maintain-wsus-part-1-choosing-your-server-os/
https://www.ajtek.ca/wsus/externally-facing-wsus-servers/
https://www.ajtek.ca/wsus/dual-scan-making-sense-of-why-so-many-admins-have-issues/