question, if I set execution.checpointing.interval = timeX before creating table and insert jobs, are that tied to those jobs, or can i later change it globally for all activity on the cluster by setting it to TimeY ?

you can set this config cluster wide i.e every time a new job gets started it will get from the specified time interval.. then you also have the option to tweak this config on the job level i.e every time you create a new job it will use the specified interval. but if the job starts (i.e insert into) you can't change the interval.. you will need to stop and restart the job.