ESIGN only applies when you need e-documents to become the legal equivalent of paper. That need arises when two conditions are met: (1) the paper documents contain federal disclosures of some type, and (2) the federal law or regulation that requires the disclosures also says they must be delivered "in writing."
ESIGN functions like a license. Once you have obtained a customer's consent (in the ESIGN-prescribed manner), regulators and courts must view your e-documents as "written." You can also obtain ESIGN consent for documents that don't have to be "written", but that's totally up to you.
The short answer to your question is "it depends." Compile a list of every notice or other customer communication you want to e-deliver. Then, review each item individually. Determine if it's required by any federal reg. If not, then that item can be handled any way you want. If the item IS required by a reg, review that reg's general delivery requirements...looking for any requirement that the item must be provided "in writing" (or equivalent language.)