A built-in embed block. Squarespace's page editor includes an Acuity Scheduling block you can drop onto any page, no separate account linking needed beyond connecting the two once.
Shared billing, separate data. Buying Acuity Scheduling through your Squarespace account puts it on one bill, but it doesn't merge the two products' underlying data.
A booking page that works outside Squarespace too. Acuity Scheduling remains a standalone product usable on any website, or with no website at all, independent of whether it's embedded inside a Squarespace site.
Still a separate client record. A client who books through the embedded widget gets a record in Acuity Scheduling's own client list, not Squarespace's.