this 2FA is just simple OTP via email, right?
I can't remember all the choices but I'm using Google Authenticator (actually WinAuth on my PC).
You need to confirm the email to set 2fa but after that, it replaces email confirmation.
slow and instant withdrawal required confirmation, but weekly auto withdraw doesn't?
Correct. That is because you need to confirm by email or 2fa to change the payout address on the weekly.
Last time,
a few months ago, I asked about changing email address and myfe never said anything about setting up 2FA
I hesitated and didn't try to change my email address at that time, because the FAQ on the site stated
How can I change my Bitcoin address or Email address? By clicking on the button that says
PROFILE in the top menu. You will be able to change your email address only if the email that is currently attached to your account is invalid or it is bouncing our emails back.
Hmmm. Not sure about that, maybe the FAQ needs updating. I haven't ever changed my email but wetsuit specifically told me that to change the email address, a user needs to have 2FA enabled which requires verifying the old email first.