Are Keyboard Text Substitutions - Text Substitutions.plist - stored and shared via iCloud

Are Keyboard Text Substitutions found in, for example the file Text Substitutions.plist stored and shared via iCloud?

If so, how often are the local and shared data polled, updated?

Is there an upper limit to the size of the file Text Substitutions.plist?

Does this make sense?

My purpose is to maximize the deployment of the keyboard text substitutions in an efficient high-production, high accuracy keyboard entry.

Short range objective: To arrange a "Type Off" challenge with Siri with respect to accuracy and speed.

Thanks.

Alan