How to deal with mapped domains and SSLs while Scaling or Moving Multisite

How to deal with Mapped domains and SSLs when we scale multisite installation?

I will be using letsencrypt SSLs to cover mapped domains and wildcard SSL to cover subdomains. When I want to add two new servers, how do I approach this issue?

Domain mapping works on setting an A record to specific IP right? Any insight or help is very much appreciated. Thanks.