how private?

Gimmwinkle gave you some good advice. However, the memo feature in chat isn't exactly completely private. The person running the site can see all chat text, including private stuff. This is actually a good feature to prevent abusive nibble nuts from things like trading risky links, etc. Personally, I've also always just presumed the chat is monitored by govt agencies, so I still wouldn't say anything too revealing even though I trust our own tech folk.

I don't think there's a waiting period to get into Lifeline chat, although that is only open at specific listed times during the week. There's a link to it at the top of the page.

There are other good email servers similar to Protonmail. You can find serious reviews of them. Just don't post your address publicly. It gives bored antis with hacking skills something to focus on. And never ever EVER use the same email address for any other part of your life.

You're probably not actually new to this, but just saying it in case you are.