Before which point must it be done ? I wouldn't like to lose my account 
...
...I assume the answer to that is as soon as possible.
2FA is only for people who can't keep their passwords safe. It should be optional. I don't see a plus in requiring a working e-mail address. It reduces privacy.
I fear the new forum will make intensive use of JavaScript, which is a nightmare for any speed / security oriented user.
I fear the new forum will make intensive use of JavaScript, which is a nightmare for any speed / security oriented user.
No, 2FA is for everyone (at least for everyone worried with security).
You can have an anonymous email address and only use an address for the forum, many people do that (hence the warning for verifying if the email address is valid. And because many people use a fake one too).
You can already see on the beta website how the forum will be (more or less). I've tried it a few times and I don't think it's slow.