There are only few differences between the free Google Tag Manager version and GTM360. This is probably also the reason why this product of the 360 Suite is not sold separately as an independent product, but is only offered in connection with Google Analytics 360 as a free additional service.
The few differences to the free GTM version nevertheless offer some interesting advantages for larger companies:
Service Level Agreement (SLA)
Similar to Analytics, Google only offers support and a service level agreement for the 360 version of Tag Manager. See the SLA terms and conditions at https://support.google.com/tagmanager/answer/6357156
Unlimited number of workspaces
While the free GTM version allows a maximum of three workspaces, the number of workspaces in GTM360 is unlimited. Workspaces facilitate the simultaneous collaboration of multiple users on one container. So you can configure changes in a workspace separately, test them and publish them at a later time. Updates that have been implemented in another workspace can be synchronized with your own container. In any case, this is a useful feature when several parties edit, test and publish container updates.
Workflows with approval
In the 360 version of the Google Tag Manager there is also the possibility to handle the container update workflow more strictly. A user can configure updates in a workspace and then submit them for approval. Users with "approval" rights can then confirm these changes and finally with "publish" rights can put the new container version live.