Domain Mapping

Hi, I’m trying to use WP Multisite Network with top level domains. You will see the primary and secondary domain in my account. They are new sites so I don’t need a backup. I believe I followed https://wpmudev.com/blog/how-to-build-a-wordpress-multisite-network-with-multiple-domains/ correctly, but some of the information is either out of date or incorrect.

I have some questions:

1. How should domains be added? Network Admin -> Settings -> Multi-Domains instead of Network Admin -> Sites -> Add New I suspect.

2. Can Cloudflare be used with Multisite?

3. I get a “connection not private” warning in Chrome when I browse to my secondary domain. When I bypass that warning I get the cPanel error page, https://secondary-domain.com/cgi-sys/defaultwebpage.cgi. How do I fix both of these issues?

Thanks.