Should I use smaller text or all caps to fit more into smart glasses?
Shorten and organize the message first. Smaller type can make the content harder to read, and all caps is not a universal solution to limited space. Preserve the detail the wearer needs for the next action.
Rewrite before compressing
Our preference is to remove introductory wording and repeated context before touching text size. A display card usually does not need a sentence explaining that it is a notification. It needs the event and the useful detail. For longer content, offer another card or a handoff instead of shrinking everything.
Compare the invented messages "We would like to inform you that your meeting has been moved to room 4" and "Meeting moved: room 4." The shorter version preserves the actionable information. That is a content improvement the optics cannot make for you.