Apart from the mentioned sources to register the data you want to visualize, we also provide customized dashboards wherein the data used in the charts and dashboards is indexed and synced from the provided API.
For example, here is a project we did with Metapool to build Near Staking Dashboard
Where they provided the API as a data source
Which we indexed day wise into various network metrics
And DappLooker does the science, showing you the end result as the Metapool Stalking Dashboard
Please see below, how projects are using off chain APIs with DappLooker