This new feature changes the syntax of how (multiselect) option sets are accessed via PowerApps. In particular the _*_label thingy is not necessary anymore with the new features. So the syntax of my former piece of code from above changed to
with 'PowerApps Align' being the name of the global option set used in Dynamics to represent PowerApps behaviour.
However, this new version using new CDS option set features does not seem to work offline anymore while the older version without the new preview feature does. I tested this on my phone using PowerApps in airplane mode. I am guessing that 'PowerApps Align'.Left etc needs to be read online from the server.