It is a good general practice to create and edit your geometry before creating labels. This applies to plots as well.
When you externally reference plot data, you can add labels to them in the current drawing. You can label plot xrefs in the same way that you would label any object. It is recommended that you do not apply labels in a source drawing that you will be externally referencing because these labels are not editable. You should insert xrefs and then label them in the current drawing. If you want to add plot tables, you must first convert the labels to tags.
For managing projects with plot data, use plot external references. Vault does not currently support plot data so you must use plot xrefs to input source data into your current drawing.